This is just a general impression, but I've found that the French aren't terribly sympathetic toward anything considered an "allergy." That's starting to change, but change comes slowly to France.

A German friend of mine has one of her sons on a wheat-free diet (whether or not he is actually allergic to wheat/gluten or anything else is uncertain). At school, in order to bring his own lunch to eat in the cantine, they require a doctor's note regarding his need for a special diet. Otherwise, eating the "French food" on offer is considered part of the education process.

There is an association in France for those with celiac disease www.afdiag.org - Le site sans gluten ! You might be able to get more information there.
Cheers,
Bev