Cyber, I think it would depend on the pack that you choose.
DS has been in Beavers and cubs, and they have welcomed in a couple of children with disabilities very well, one who is profoundly deaf, and one with pretty severe ADHD behaviour, which our leaders have coped with well, and enthusiastically. The deaf boys parents take it in turn to attend meetings, so they can sign for him (altho cubs have started to learn BSL so they can help him too), and our cub pack paid for them to get CRB checks, so they can help out on camp etc (they help with all the kids, not just their own son).
But my guess is that it would depend very much on the leaders, and the size of the pack, you would be best visiting the packs nearest you to talk to them first. The scouting association generally is trying to be as inclusive as possible.
What your DS would get out of it depends on him and you. If he can socialise, then obviously it is an advantage in that he meets new children. He can start to earn badges for some of the activities, so he would know he's achieving. Our packs go on visits (RAF Scampton to meet the Red Arrows recently), hikes, camp (one or 2 night camps only in beavers/cubs, longer once they reach scouts), basically it would just broaden his life experiences.
You/your DS would be able to go along to 2 or 3 meeting without committing to buying uniform or anything, to see how it suited you, worth a try.
Hope that helps.