Dh has 3 brothers and 2 parents and I think every single one of them has ADHD to some extent. First time I went to Dh's house, there was a motorcycle parked in the living room. All of them are extremely passive and laid back. The parents obviously care about their kids but have a very hands off approach, with "happieness" being the goal. Let's just say that of the 4 kids, one of them was living with them til he was practically 30. The other 3 got married young to wives who took control and whipped them into shape to the degree that that is possible. The one who lived there til almost 30? The wife was there too for the first few months of their marriage, and now they are in their mid-thirties, would like to start a family, but cannot because they are in low wage jobs. BIL was in college for years but kept flunking or dropping classes and finally dropped out. He tried again recently, same thing happened, apparently. He doesn't stick with anything. So in his case, the hands-off laid back approach did not work. He never got his act together. He has a gifted level IQ, was a national merit scholar (or semi-finalisit?), and never got a degree.
Also....right now your DS is at an age where you can force him to do things, but in another few years that may not necessarily be possible. So I would start now. I wouldn't go over the top and make him miserable or stressed, but find some balance. We are dealing with the same thing. DD really wants to keep taking piano lessons but the practice is like pulling teeth. She wants to be in an advanced math group but then doesn't want to do the homework. Same with DS. I don't want to be "pushy" but don't want them to to turn into sloppy, lazy adults either.