Largely threading the needle between Disney Channel’s tween audience and family members who will relish its ties to the broader Disney fairy-tale universe, “Descendants” is a playful and tuneful TV movie, exhibiting much higher ambitions than, say, the “Teen Beach” franchise. Granted, one might wish the focus tilted a bit more heavily toward the adults — Kristin Chenoweth as Maleficent steals every scene she’s in — or that the second half wasn’t as heavily padded. Still, the songs are clever, the look is sumptuous, and the idea is so good it goes down easy even if the broth’s a trifle undercooked.

More earnest than something like “Once Upon a Time” but plucked from the same set of ribs, “Descendants” begins with the premise that the defeated Disney villains have been relegated to a sort-of exile in a place called the Isle of the Lost, where they have been confined but are free to raise families. (Never mind that they all seem to be single parents or had one kid at exactly the same time; nitpickers, begone!)

Growing up without magic, the kids kick off the festivities by singing an energetic number in which they embrace their family lineage, “Rotten to the Core.” But then four of them are chosen to attend school alongside the good kids, who live in the glittering kingdom of Auradon, where Ben (Mitchell Hope), the son of Belle and the Beast, is about to be crowned king.

So into this strange environment come the children of Maleficent, the Evil Queen, Cruella de Vil and Jafar — in sequence, Mal (“Liv and Maddie’s” Dove Cameron), Evie (Sofia Carson), Carlos (Cameron Boyce) and Jay (Booboo Stewart). Alas, Maleficent dispatches them with plans of stealing the wand of Fairy Godmother (Melanie Paxson, also a hoot), thus paving the way to unleash the sorceress back on the world.

“Descendants” thus engages in a somewhat predictable nature/nurture argument, with the four transplants starting to like their new home, while Mal — initially the most committed to the notion of DNA determining destiny — gradually beginning to fall for Ben. And while there are obviously thick strands from Disney’s animated classics woven into the story, the borrowing goes beyond that, including a bit of Harry Potter, including a game that looks like a hybrid of Lacrosse and Quidditch.

Written by Josie McGibbon and Sara Parriott, and directed and co-choreographed by Kenny Ortega, the movie boasts a stronger, more assured story than most of the recent youth-oriented live-action musicals Disney has offered, with plenty of brightly colored bells and whistles as well as songs that range from Broadway to rap. About the only cautionary note is a climactic sequence that might be scary for some young kids, given the difference between CGI creations and full-blown animation.

Fortunately, parents who might have been tempted to seek shelter elsewhere from these exercises in the past will be compensated, principally, by Chenoweth, who clearly embraces the opportunity to cut loose with her “wicked” side.

While such brand extensions always require care, Disney has been adept at wringing additional mileage from its old fairly tales and movies, including preschool titles like “Sofia the First” and “Jake and the Never Land Pirates.” And while there’s always the risk of sullying storied franchises with such offshoots, in the case of “Descendants,” at least, the studio proves they can do some good without being bad.