Personally, I would not serve the food. It sends messages to the kid that they are not expected to get along with what the group is doing or eating etc. Daycare is group care and that means everyone does the same thing, eats the same thing as the group each day.

Besides, it is a pain to have to get separate foods out and then explain to others why they can't have some. And then there is the fact that you don't personally know what is IN that food brought from home. If another child develops an allergy because they swiped some of their friend's food then that is an issue too.

Just say NO.