What do you do about social issues?

Here is a question. My son is upset because he never gets invited to birthday party's or on play dates or sleepovers. I think part of it is that the parents are not sure what help he needs and since he is in a wheelchair full time at school, they don't realize that at home he can get around just fine without the chair. They feel like if thier house is not accessable then he can't come over. I think they also don't know what he can and can't do. The other issue is that he is very immature in many ways and not good at making friends. He spent so much of his early life conning adults that he did not learn how to make friends with his peers. He was treated differently from the kids so they did what he told them to do trying to get into the good graces of the adults. Plus he was more mobile than most and would do mean things to them. Anyway, he has very few friends as a result. But even those few don't invite him. We invited the entire grade to his birthday party and only a couple came. Right now things are so busy with different kids that I don't have time to have a kid over, but I plan to try inviting his friends over with thier moms when things calm down. (After football season!) Do any of you have this issue and what do you do?