Re: "Appropriate" affection
DD's school teaches the kids about needing space from a very young age. From day 1 of DD's transition to her new school, one of her classmates was constantly in her face and sitting or standing up against DD. So, at 15-16 months old, DD learned to put her hand out and say "No thank you" to her classmate. The teachers would then say to the classmate, "M wants her space please." After a while DD started to say, "No thank you. I want my space please." The teachers teach all of the kids this and now, the kids respond really well to each other's requests for space. Maybe you could teach your son that people need space and when you see a child resisting his interaction you could quietly say, "I think this little boy/girl wants their space."