So.... we attempt to modify recipes as much as possible to make them healthier (whole wheat flour, fruit-sweetened instead of sugar, etc.). I also contact the families to let them know what we will be preparing/serving. Our conscientious mom will often modify the snack on her own and send it along for her kids. Inviting those who have food issues to help modify recipes is a great way to get them involved.
I think it's important to be aware of this and to recognize that obesity is a HUGE problem in our country and it is affecting younger and younger children.