Have they gotten sick frequently and miss a lot if school. Accommodations need to be reasonable to the student and illness. I think anything relating to food, cross contamination is important and perhaps a health class should be done to teach kids about Celiac, so they can both understand it and that they cannot catch it. It is best for teachers and cafeteria workers to know about this too. It is also important that the teacher leave instructions for a sub, where there to be a party or holiday celebration. I'm not sure about the need for an extra set of books, unless they miss a lot of school. I think every parent would like that for their kids. Just have the 504 focused on each child, the illness and try to anticipate issues. The 504 can always be amended. You don't want it to become a stigma so your kids will potentially be sources of bullying. Good luck.