Which valentines treats can I give my class if one child has celiac disease?

Ask the parent. Why give food or treats for valentines day? There may be children with other food allergies or sensitivities that you are not aware of. Consider non food activities instead. If you still must have food, then please contact the child's parent(s) and seek their advice. They know what affects their child.
Celiac. Two options: got to foodallergy.Org for gluten-free recipes or make normal treats and ask celiac pupils mother to make something gluten-free that the child likes and have that for the child.