Oh yuck - what an annoying way to start the day! I'm with 5 Little Monkeys in that going forward I would ask that the parents provide all the food for the child. It can get very expensive to accommodate a gluten-free diet and then what if another child develops a milk allergy for example and the next thing you know you have all of these crazy dietary restrictions to accommodate - lots of work and lots of money.
For today you could go with rice and veggies? Fruit? hummus? Apples & Bananas (see what I did there ;-))? Good luck!