I am going to offer advice/suggestion that may upset some. Please keep your child out of contact sports. Running, swimming, tennis & golf are great options.
Why do I say this ? I am NOT a medical person, but I was a boxer, wrestler & football player. As a high school student I not only was an amateur boxer, but was a sparring partner for local professionals. I wrestled for a very competitive team & our football team was easily among the top 5 in the country. I experienced serious physical contact on a daily basis for years–but never once was diagnosed with a concussion. This leads me to believe that your son is quite susceptible to concussive head injuries. Contact sports & the risks of a second and third concussion & depression later in life are not worth it. Squash & racquetball are two other sports in which concussions & physical contact is rare. Water skiing also.
Sorry for being preachy, but head injuries are serious business. Just try to get into the US Air Force pilot training program with a former neck injury, for example.