children dont play with other children until about 3.. so i wouldnt be to worried about that side of things he will play eventually (when they are doing something he likes)
if you are overly anxious that is where he is learning those behaviours from, you might step back in a group so he steps back to he is coping his mummy(his favourite person in the world)
maybe ask at his next check up but i think it is just the type of child he is! sensitive to change, loving and affectionate in his family group!