J.S.
M.,
My son is in the Roseville school district, and is signed of for an ECFE preschool for fall. He has a peanut allergy (not as severe as your sons). But, the school district is very careful and very aware when it comes to allergies, since they are so common these days. I suspect that as you call around, you will find that the schools are able to help you out.
For example, they use home made play dough in the classroom at ECFE (not sure if it is wheat free though...). Snacks come from pre-approved lists for the class (allergies accounted for).
You will have to start him in school in a few years, this is a good time to get an allergy plan together with your pediatrician (or allergist) and start working with others to help him understand his allergies.
Good luck.
J.