We're in Disneyland Paris, and the cavernous foyer of the four-star Hotel New York is a twinkling wonderland, with jolly families bustling hither and thither. Standing in the middle of it all is a devastated-looking man; he's in his late 40s, with a sallow complexion and dark hair. He turns and a large, square portrait of a cherubic teenage boy's face is revealed on the back of his T-shirt. It's the sort of image you'd see on a missing person poster, or a fundraising campaign for a terminally ill child. He ambles past. "Tobias Saltman, 17, multitalented and availble [sic] for work," proclaims the large print under the picture. A dad prostituting his son? What on earth is this?

This is Growing Talent 2008, aka Europe's premier talent event, an idea imported from the United States. For six days, children aged four and upwards gather at the hotel's convention centre to show off their acting, dancing, musical, comedic, modelling and television presenter potential. There are workshops on dancing for Broadway, how to audition and microphone techniques for singers. There are seminars with intriguing titles such as Your Child and the Biz and From UK to Hollywood. But the real action takes place in the hangar-like auditorium, with its huge, white-lit stage and catwalk, where each of the 300 participants does a two-minute turn in front of a panel of judges to win a place in Saturday night's talent show.

Parents of a certain generation, me included, recall with horror the 1970s children's talent show heyday, when Saturday night programmes such as Opportunity Knocks launched the careers of Bonnie Langford and Lena Zavaroni, and granny was reduced to tears by St Winifred's school choir's Grandma song.

But today, what sort of parent would want their child to be embroiled in the desperate world of showbusiness, let alone foot the £2,500 per child bill (including fees, travel and accommodation)? What brings them here?

"The contestants come to get noticed," explains the event organiser, Lynne Millar, who has a theatre school in Glasgow. "They are meeting professionals they wouldn't get the chance to meet otherwise. It also has educational value: they attend workshops and get good advice. They come for the competition, but the awards aren't indicative of success. The parents take away a higher knowledge of the business."

Most three-year-old girls flirt with the idea of becoming a ballerina at some point. Grace Key from Middlesex was that age when she spotted Fizz doing a clumsy arabesque on the Tweenies and told her mother that she too wanted to be a dancer. Now aged 11, and a big Hilary Duff fan, it's an ambition she has yet to relinquish.

"Her dad and I thought that if she comes here and enjoys it, even though it's hard work and stiff competition, then we'll know it's worth her pursuing her talent," says her mother, Michelle, "and it justifies all the fees we pay for her classes. It helps us know that she is serious about what she wants to do and we'll support her."

"It's her dream," beams her proud granny, Vera.

"I just like being on stage," says Grace. "It feels like it's where I belong," she adds, with a toss of her long brown hair. "I'm coming back next year."

T-shirt dad, aka David Saltman, 49, from Hertfordshire, is getting over his disappointment that his actor/comic son Tobias has not been selected for the talent show finale. "This is an opportunity to get into the career I want and meet all the VIPs, the big cheeses," chirps a charismatic Tobias, who has attended drama school since he was 11 and whose acting credits include CBBC's MI High and a KFC advert.

"It's been hugely expensive to come here," says David, "but it's a drop in the ocean compared with what we've spent over the years, nurturing his career. Since he was seven we would take him to open auditions - and you'd lose a day's work. And we put him through theatre school, which is not cheap for an ordinary jobbing guy. But at auditions you'll meet one casting director - here there's a dozen. He's getting 18 months of auditions crammed into a week. And let's just say we're making the most of the breakfast buffet."

Loitering outside the auditorium is Eden McAllister, a nine-year-old Scarlett Johansson lookalike from Belfast, and her mother, who is going through the steps her daughter is about to perform in the dance showcase. "We'd love her to go to stage school," says, Amanda McAllister. "We're hoping to make some contacts. Eden's a fantastic dancer."

What does Eden love about dance? She thinks hard and brightly offers: "You get big trophies. I've got 36."

"Eden!" interjects Mum. "She's been doing gymnastics since she was two and is on the Northern Irish squad. She's also entering the modelling showcase. If they've got a talent, it's worth nurturing it. You want the best for your children. I own a children's beauty and hair salon and she also models for that."

The atmosphere is chock-full of exuberance bordering on demented. Children with ants-in-the-pants nervousness line up against one wall waiting for their two minutes of dance glory on the main stage. They wear a dazzling array of multicoloured garments: tight, lurid Lycra is popular, and many hours have gone into the lovingly embellished homemade costumes. Bowler hats are worn, canes carried, boas flourished.

Sitting on the judge's panel is an impressive array of children's showbiz personnel, among them directors, agents, modelling scouts and casting directors. Seated at one end is Barbara Speake, of the eponymous theatre school. She is 79 and looks marvellous in a velvet alice band and festooned with ornate jewellery. Beside her, equally blinged-up, is her business partner, June Collins, the mother of Phil Collins, the drummer. She is 95.

Beside them is Kenny Cantor, of Cantors Theatre School, resplendent in glasses Dame Edna would reject as too ostentatious. The casting director Pippa Hall (her credits include Billy Elliot and The Chronicles of Narnia), the children's agent Mark Jermin, the National Theatre and West End director Paul Jepson, and the actor/writer/casting agent Sarah Counsell (she has been in Skins and Tess of the D'Urbervilles) sit bonding and gossiping.

Spectating is agony and ecstasy. Eden impresses with her sylph-like grace; the boy in combat gear doing ballet has chutzpah, as does the black girl in a white mask doing in-your-face hip-hop; lyrical dancers so passionate that an audible "aww" ripples around the auditorium; and the contortionist who can peer up her own undercarriage. But there is also the truly awful: the group routines let down by the flailing, clumsy one at the back; the clodhoppers with fixed grins and jazz hands; and the South Bank Show theme tune used for a tap-dance routine. Everything is greeted with raucous applause by the watching parents; the cheesier the routine, the louder the response. It's rather touching. But are they all, well, a little delusional?

"It's up to the parents if they want to come, but the children shouldn't be passing auditions if they're not up to scratch," says Pippa Hall. "I have to be honest about their ability and not give false hope. There's a big difference between the bright ones that want to act, say, and the ones that want fame, the bling-seekers or the ones who are doing it because they are no good at maths."

Mark Jermin offers this advice: "As long as you enjoy it, keep at it. Obviously, not all of them are going to be the next Daniel Radcliffe, but if the competition gives them self-esteem, then great. I honestly believe there is a job out there for every single child. At the moment I'm looking for a chubby child and a child with a squint, both for soap roles. Every child is unique. OK, so some are more castable than others."

"Everyone says Tobias is amazing," says David Saltman. "But in fairness it's hard to tell if they are just being polite. In our opinion he has talent. Go on, do your Jim Carrey," he says to his son. With this, the multitalented Tobias breaks into a bang-on impression of Carrey in The Mask: "Somebodddy stopppp meeehhh!"

"I am immensely proud of everything Tobias does. Why have children if you're not going to support them and give them all they want to do? The T-shirt was my wife's idea. She had seven done; one for each day. It cost £50, a rush job - they spelt available wrong. At first I said, 'Do I really have to wear this?' and she said, 'Yes you do.' I'm not that happy about it, but it's his dreams, so whatever it takes."

And how does Tobias feel about his dad's sartorial cheerleading?

"I was horrified. I couldn't believe he had actually put it on, I guess he was scared of disobeying Mum. I begged him to stand against a wall, but then a few of my mates thought it was wicked; they keep pestering Dad to give them one. So I'm now appreciating it, but ironically obviously."

By the time the week rolls around to Saturday night's talent show, nerves are frazzled. The children have been following an intense routine of practise/rehearse/perform and waiting for their name to appear on the magical flip chart indicating they've made it through to the finale. Hardly anyone has left the hotel for days. I wonder how the children are coping.

"There have been tears," confesses 18-year-old Kate Finegan, from Dublin, her curly brown hair bobbing, eyes wide with the excitement of it all. "This is such an emotional rollercoaster. You go from the buzz of performing to feeling beyond devastated when you don't get through. But I've got three callbacks [when a VIP asks to meet you one-to-one] so I'm over it now."

"It sounds corny, but everybody is crazily supportive of each other," says her friend, Ciara Lyons, 16. "There's the odd stage-school brat who thinks they're better than you, but most kids here are normal and friendly."

OK, so brats may be thin on the ground, but what of that most hideous of creatures, the pushy parent? Surely the place must be teeming with them? "I saw a four-year-old crying because she didn't want to go on stage. Her mum was trying to bribe her with the promise of a visit to the toy shop. It's not right," says Pippa Hall. "That's when you know it's all about the parent, not the child."

"I am the quintessential stage-school parent. We all are, otherwise we wouldn't be here," says David Saltman. "Look at me, I've got a T-shirt with my son's face on it! And I can't tell you the number of parents who've come up to me and said, 'Ooh, I wish I'd thought of that.'"

Barbara Speake is relaxing with June Collins. "The thing I don't like about competitions is that it brings out the worst in the parents," she says. "Does it matter where your child comes for goodness sake? I always remember Margot Fonteyn: when she was 10, she entered a ballet competition and came second - whatever happened to the girl who came first? You don't perform for your own gain, but to give others pleasure."

"You must be a very proud mum," I say to June.

"Oh, they were only ordinary children," she says.

"No they weren't," pooh-poohs Barbara. "Clive's a cartoonist, Carole was a brilliant ice-skater, in all the shows, and Phil we all know about. Phil was always special; aged five he entered a Butlins talent contest singing Davy Crockett, but he stopped the orchestra halfway through to tell them they were in the wrong key."

June says, "You can't bring children into the world and go, 'Right, now that you're here you're going to do this and you're going to do that.' You've no right to - it's their life and they've got to make of it what they can."

A couple of hours before Saturday night's talent show starts, a primitive rumble comes from deep within the convention centre. The sound of drums and incessant chanting can be heard. The foyer is packed with gangs of children, hundreds of them, involved in a mad jungle boogie. Led by the bongos of the Young Persons Theatre Company, the children dance frenetically while making "Heads, Shoulders, Knees and Toes" sound funky.

It's an entirely spontaneous happening, of the children's own making. They are not being judged, auditioned or compared and they are having the time of their lives. It's like something you would see stumbling into Glastonbury's Green Field at dawn, one of the most creative spots at the festival. A couple of teenage boys jigging about are wearing Tobias Saltman T-shirts. It is quite the most fantastic children's show I have ever seen.