I would suggest Assassins Creed, Black Flag is the new one, which still has some violence and bad language but not to the same level as GTA. Watch Dogs is out in spring which is also open world and expected to be a big hit. Just Cause 2 is good fun but quite out of date now. Far Cry 3 is also good for open world, though he might complain that the online isnt open world like GTA, just deathmatches. But its a great open world single player game.