My kids do model ling do you think they are too young? They are 7,5,3 and 2??

As long as the kids are allowed to be kids, are not being worked as adults and enjoy what they are doing I think it is fine. You are mommy, trust your gut and don't let money, status or image blind you. If you think one or all are unhappy then step in and be mommy first and foremost:)