The first thing is that you can expect that he will be able to snowboard following a reconstruction. I would avoid the patella tendon graft option as this can leave you with potential patella tendon issues in a growing child. The operation is only part of the rehabilitation. Without an ACL the brain lacks some feedback/feed forward information on what is happening at the joint. The joint is also lacking some of it's rotational stability and normal functional movement. A firm (as opposed to slack) graft is important in the first instance. Then a large amount of proprioceptive retaining is required to maximize the function in the leg. The more of that your son does, perhaps the better the outcome.

As one surgeon said to me once..."You can have great surgery with poor rehab and have a poor result, you can have poor surgery and poor rehab and have a poor results BUT you can have poor surgery but great rehab and gain a good result"... It was anecdotal but the message is clear that the rehab is more important than the surgery.