7-08 with reduced recoil loads and a rifle that fits him sounds like the way to go. Good luck with your search and try and get his hands on as many rifles as you can and pick what he likes. I have as much fun researching and shopping for rifles for my kids as I do for me.
Have 2 daughters that hunt. Older is almost 13 shoots a 243 and right now doesn't want to try anything bigger. Younger just turned 11 shot her first deer last year with 243 and her deer this year with her 6.5 Grendel. Younger is quite a bit smaller but will try any of my rifles I will let her...