If you do decide to let him take it, make sure he knows NOT to drive to
the next exit nor to the top of the present hill should the oxy/alt
light come on.  Rather that he knows to shut off the engine right now
and coast to the side of the road and check to see if the belt is still
in place.  The waterpump, after all, is driven by the alternator belt.

If the belt is OK then he could drive on the battery for quite a ways to
get to where he could have the alternator repaired.

BTW, in a pinch, one can shift the power steering belt to the
alternator/waterpump.  It won't hurt the power steering to go beltless.

It wouldn't hurt to make sure he knows how to change belts and do other
routine maintenance things.

Mike