One other comment: if your son doesn't appear upset by the current group dynamic, it may not be as much of a problem as it feels to you. As parents, we sometimes take our children's experiences to heart more deeply than they do. (The opposite, of course, can be true.) I can remember being out when one of mine was very young, and hearing another child say they didn't want to play. I was heartbroken for my child, and consequently a little shocked when my child's response was to say a calm "okay", turn away, and happily find something else to do.
