My advice would be to walk him through a full body circuit, 3 days per week for about 2 months. Have him concentrate on form and really ingraine the basics into his head. He is young and untrained, and will make a lot of natural progress.
You can also have him jog one or two days per week; go with him as a bonding experience. This is not great for gaining mass, but he will need the aerobic endurance as a wrestler; also, should he choose later on to follow a body-builder type lifestyle, having a good "cardio ethic" will be invaluable to him.
Once he has learned the basics, you may want to look into something more specific for his sport. I would think that Renegade Training would be a good option.
As for the creatine, I am not an expert, but I doubt it would do him any harm. Along with a good protein powder, those are the only supplements I would even consider for him at this time. Food is really what he needs, and lots of it. It he's eating a lot of meat, he will be getting loads of creatine, anyway.
Good luck with your son, and hope this helps.