For deer and elk, I would suggest a 300 Mag / 300 WSM....versatile caliber from light loads of 100 grain to heavier 200 grn bullets. You won't find those in .270, 7mm, etc. If you're gunnin' for deer and some elk, probably a 270 or 7mm....Elk and some deer, back to the 300. Since it is assumed that you're son is at least 18, I would assume that too much recoil shouldn't be an issue. However, wanting to concentrate on accuracy and maybe even work up a load will take some shots on the shoulder so, gearing down to a 30-06 may be in best interests. I have an -06 which I cut two inches off. Takes the velocity down about 100 FPS (if that) but I still retain the versatility of the .30 cal and also, have a sportier rifle for carry in the brush.