I agree that mom should have brought food. If she is concerned, she needs to take on that responsibility herself. I have celiacs and would never eat cheerios. I can't eat oats unless they are certified gf. Same with rice. It needs to be gf. The longer I am gf the more sensitive I am.

If there is concern, I think it needs to be put on mom to provide the food. Gluten is in so many things that you wouldn't even suspect and cross contamination is a huge concern as pp said. For that reason, I can't/won't do bulk barn.

So, while it can be done, it's not easy and it's not cheap. Put it right back on the parents. Good luck!