Why won't DS go to other people's houses?

[JimWilsonBell]

My DS is 13 and has ADHD. His father my ex is socially very awkward. I'm very sociable and so is SO. We are off to a works family bbq today and DS is flatly refusing to go. He always does this and it makes me sad and mad at the same time. I have tried telling him well in advance and keeping it til the last minute. I end up making bloody deals with him or shouting and getting upset. I'm not happy to leave him at home on his own, I know the law is grey about this. All he wants to do is lie in his bed watching bloody YouTube. Help!