I would recommend that your son perhaps joins a club such as cub scouts here they encourage good interactive playing and socialising in a caring enviroment. By looking at how other children interact at the club he should be able to pick up good social skills. Also invite friends and their children over to your house or go out with friends and their children or family to parks , also if you play with him you can teach him how to play well!

Myself and my husband do play games with him, hes our child its what you do when you have children. We dont have any friends who have children yet and the ones that do are babys. He used to go to beavers but didnt like it so left, we may try sending to scouts and see what happens.
Thanks