From a medical standpoint i have no idea how bad of an idea it is. If you want to have fun with him and continue to challenge him there are plenty of easy pieces of equipment he could start on. Doing jumps and weaving may not be ideal, but running through tunnels and chutes and walking up frames could be okay.
As long as the instructor and your classmates know he's not 100% and you take things slow. Have you spoken to the instructor to get his/her thoughts? They may steer you away from classes for a little longer.
As long as the instructor and your classmates know he's not 100% and you take things slow. Have you spoken to the instructor to get his/her thoughts? They may steer you away from classes for a little longer.