Being in social situations with other kids is very important for children. They start to learn social skills, learn how to play with others, and how to behave. I wouldn't worry too much about your little ones being handfuls. Most children are and I am sure the teachers at bible school are trained to know how to handle them. Take the time to get things done for you, feel good about the time you have alone instead of guilty that you're not there with your children. Bible school is a good transition to when they go off to school full time.