Lot of good advice here. I'm very much in the camp for letting him come to his own conclusion about what he'll pursue.
One of the principal reasons? As he progresses in a sport, the need to work only heightens because those who remain in it are increasingly the ones who are devoted to it. If his passion for a sport at a younger age dwindles, he's either got to return to it because he discovers that he can't live without it or find himself even more challenged down the road by the increasing proportion of ones who are genuinely dedicated to it.
Best of luck to him!