they should be playing every play worrying about the possibility of another concussion.

If it's really that much of a concern then if it was me, I just wouldn't play. I imagine the coaches are willing to let him push it, but also tell him to avoid certain situations. Then the longer he's able to go with no concussions probably the more willing they are to let him go all out with the reason being that it is no longer a big concern.

But - if he has another concussion in the future they'll need to take a very long look at whether that want him to continue playing or not.