By all means the 30-06. Everything else mentioned would be a compromise and not make a good all round gun. Expecially the 30-06s weak brother the .308. The 06 is capable of taking anything in North Americia, yes even the Coastal Brown Bears of Alaska. I would start him out with the reduced recoil loads, they are fully capable of taking a Black Bear. If he never shoots anything but Black Bears and Deer he will have a gun that will last him a lifetime. If he decides to get into hunting in a big way, he will have the gun to do it all. I shoot everything from Cayotes to Moose with a 30-06.
Yes I own a .308, haven't shot it in over 25 years. Good Deer and Black Bear gun, but too weak for Moose and Grizzlies.