This is one of my biggest struggles with using rotation curriculum. We are not a small church and we have more than 10 kids that are regular attenders that have life threatening allergies. The "processed in a plant" can even pose problems for us. I have implemented a sign off sheet for parents to approve the food being used during these weeks, but it is a struggle. The parents of non allergy kids are irritated by it, and the parents of allergy kids are still nervous.
I also deal with a large group of "natural food only" parents. Any processed foods are not permitted for their children. This in turn ends up being several kids in each class who are not able to participate, for one reason or the other. Just not sure if it is worth all of the hassle!