I am a high school bball coach at a school with smaller student body, so many of my players also play football.
I would recommend that you have great communication with your son so that you know what is happening with him physically ... there's a difference between hurt and injured ... sometimes that line gets blurred especially by some players and coaches. You should communicate frequently with the trainer make sure he/she has a line of communication with your son and also directly with yourself.
Little things can become bigger things if not addressed. Often times players compensate physically for injuries and end up hurting themselves elsewhere. I would also meet ahead of time with the football coach and make sure he knows your son is a bball first kid ... that recruiting visits, workouts and fall leagues ... may occur and that there needs to be a balance.
Having said all that I am an advocate of multi-sport kids ... playing different sports helps them become more well rounded. Different coaching techniques, different learning processes, helps with the ego and instills teamwork, selflessness and toughness. Many colleges also share that opinion as well.