Sorry to hear of your son...
I would strongly suggest you purchase PREVENTIVE & REHABILITATIVE EXERCISES FOR THE SHOULDER & ELBOW, 6th Edition. It's written by "Jimmy" and his staff and will give you the blueprint for rehab and throwing program.
Currently, my son is trying to rehab from a 50% UCL tear. One director of scouting told him, "Don't worry if you have TJ surgery, it won't hurt your draft status. We consider that injury fully recoverable."