If its fun for him and he can do it alright, dont quit lettin him shoot big stuff, just dont have him sit down and shoot it a whole bunch, and probably dont put him in his own rifle that he needs to shoot a whole bunch and get really comfy with and have it be a big rifle. Good choice with the 270 WSM, its the best of all words and really kicks light.
As far as rifles, you really cant go wrong with a model 70. You can get the WSMs in a Savage and there is a lot of firm savage believers on this site, but if his parents will pay for it, i dont believe that savage can honestly beat winchester on quality. Go for tried and true model 70 "the riflesmans rifle".
My 270 WSM is a model 70 coyote, its a good accurate rifle. Its exactly what i wanted, but its more heavy varmint config. like a sendero. If he wants something lighter, winchester and also browning offer a bunch of nice WSM rifles in any configureation he could want. Model 70 classic stainless synthetic or classic featherweight might be good choices, or browning A bolt II satinless stalker(w/ or w/o BOSS, just be careful with the BOSS models because its seems to me that take an already short 22" barrel and cut it down to put the BOSS on so the actual length of rifled barrel is really short which will give really low velocities and a whole lot of muzzle blast).
If you plan on hand loading him some rounds, im workin on loads right now and could help you w/ data. Data for that cartrige is plentiful and easy to find for free. Check out www.shortmags.org
. I use 130s, but a 140 or 150 grain bullet would probably be the best choice for all around big game hunting.
Hope this helps.