We've had a pretty good track record getting basketball players to come out for track, though AAU commitments tend to thin out their availability. It's a good idea, but I have a weird concern with it:

I've actually had coaches of sports with high cut rates (and basketball cuts the highest percentage at our school) try to feel out which kids are good at track so they can sleep a bit easier giving them the axe. A couple years ago, one actually tried to get me to push a kid even harder on track so that he wouldn't have to bother cutting him. It's such a weird dynamic, but I'm actually incredibly nervous about costing any kid a spot on a team he actually enjoys.

If he makes the varsity team, though, I'm definitely doing this. Good call. Just have the coach lean on him for distance events something that will help him next year.