To call the postcard-sized creation by Whoopi Goldberg a work of art, might be pushing it, but it is still expected to spark keen interest among buyers. The work will appear along with equally distinguished ones by Bono, Benedict Cumberbatch, and Julian Lennon in a silent auction to raise funds for a primary school in north London at the annual Affordable Art Fair

Benedict Cumberbatch's postcard. Photograph: Affordable Art Fair/Rex Features

Cumberbatch and Bono have gone for self portraits – the Sherlock star's a Byronic profile, the U2 frontman's a quick slash of blue marker conjuring up his trademark sunglasses. Lennon has sent a sweetly traditional landscape in red marker on cardboard, complete with duck pond and cottage with smoking chimney, which any of the pupils might feel they could at least match in art class. Goldberg's is more a message than a painting, a cheery greeting to "all students everywhere".

The bidders will know which celebrity they're aiming for, but more starry names will be hidden among the hundred little works on sale. The comedians David Baddiel and Morwenna Banks; Jeff Kinney, the author of Diary of a Wimpy Kid; and Babybird singer, Stephen Jones, are among those providing their artistic juices.

Bono's postcard. Photograph: Affordable Art Fair/Rex Features

The postcards will be on sale for £45 each, but the buyer will only learn the name of the artist after the money is handed over – a fundraising scheme modelled on the postcard fair at the Royal College of Art, which now has buyers queueing round the block every year for bargain works by artists including Tracey Emin and the Chapman Brothers.

This time all the works at the fair, which opens on Thursday for three days on the edge of Hampstead Heath, are being sold to raise funds for the New End primary school. The fair, now an international event aimed at art lovers with lighter pockets than those who flock to Frieze or the great auction houses, has attracted more than 1.2 million visitors and sold art worth more than £180m over the past 14 years.