For your needs, I would say 'Ohana. If you avoid the alcohol, it will definitely be less than $100 and you will definitely be getting your money's worth. They do have activities for the kids, such as a hula hoop contest and a coconut race, but there is no pressure to join in.
If you want something a bit more sedate, but really good food and service, then I would recommend Kona Cafe at the Polynesian.