May I suggest fencing?
When my oldest was about three, he saw Darth Vader have it out with Luke Skywalker and spent the next few years pestering me with, “I wanna learn how to sword fight! I wann a learn how to sword fight!”
So...when he was nine, he came running into the kitchen saying, “Mommy! Come quick! You gotta see this!” It was a commercial for a local fencing academy that was running a week-long summer camp. We signed him up, and, well...that was four years ago now and he is a highly accomplished youth fencer, with a good chance at a college scholarship (if he keeps it up, stays on the Honor Roll and keeps his nose clean). One day he hopes to step up onto a pedastal and sing the National Anthem with a medal around his neck.
The sport is a good one. Its rules are courtly and courteous, it prizes agility and speed over brawn and raw power, and you have to be a neither a giant nor as small as, say, a gymnast to be good at it. That said, being tall with a long reach does give you an advantage and strength certainly doesn’t hurt.
Plus...you son will get to actually STAB his friends with a pointy (but not sharp) metal object, and nobody’s going to yell at him! What more could a boy want?
Regards,
Well, thanks, I will indeed look into it. They’ve been stabbing each other with light sabers for years.