I don't know anything about flag football, but T-Ball is a spring sport. Soccer is just getting ready to start and you can register here: www.sumtersoccerclub.com/

Your best bet is to contact the YMCA if you have one in your area or parks and recreation. If you have the opportunity take him to different events to see where his interest may be. Some advice do not spend a ton of money on equipment in case he doesn't end up liking the sport. Most importantly no matter what sport he may chose always be his biggest fan!!!!!!!!!!!!!!!!!