Coconut flour? Is coconut considered a tree nut? How about flax meal? Lots of time they use flax to replace eggs in recipes. Various gums (agar, xanthan, guar) replace gluten in recipes.

If you're looking for conventional sorts of high carb baking they use potato starch, tapicoa starch and such for gluten free baking. You can probably find forums and recipe exchanges for kids on the "Breaking the Vicious Cycle" (SCD) or "DAN" diets. Some of the SCD dieters avoid dairy too.

They're making yogurt from coconut milk these days too.

I can think of things like stews, soups and such if he can take a hot lunch to school. My Mom used to send those to school with me in a thermos. You might be able to figure out chicken nuggets using an alternative coating.

I think your best bet is to google. There's lots of kids out there with super restricted diets like that. There have to recipes...