I've had a similar situation with parents wanting their kids to have breakfast at my house. Personally I don't have a problem with it unless they are expecting me to provide the food. If the other kids see the food out I just explain that they have already had their breakfast and that's the end of it. I find that that early in the morning the kids are being rushed to get ready and out of the door. If letting them eat at my house leads to less stress and happier kids well... a better way to start the day. Like I said though, if the parents were expecting me to have time to prepare the meal that would be a different story!