My uncle has Down Syndrome and absolutely loved to ride. He spent quite a few years riding a two wheeler dutch style I suppose it all depends on the severity of the condition. He loved it but has not ridden for years as age (I think he is over 50 now) has slowed him down considerably. I hope your son can find something he loves to do that will keep him active. It seems to be pretty important (as for all of us) to stay active.