Hi S., I'm not sure where you live?? In the South Bay, Manhattan Bch, Redondo Bch and Torrance, PV area there is a fantastic group called The Friendship Circle.
Check them out online, there are social, physical activities that are created for kids with disabilities and typical functioning kids to pair up and have fun together. Beach activities, going to the pier in Santa Monica, baseball games, riding the Metro to the movies, etc. and many of the kids like to join the challenger leagues for sports too. There are lots of things to do, I know a SeaLab event is coming up. It's free or low cost and very well run. Jason is the director and you can get his contact information on the website. My son is 18 and has been active for about 2 years. There are activities for younger children too, you can dtermine for yourself what would work for your son. They support students from the HS in the area to have friends at school too. take a look, send me a private message if you want to chat about it. D.