I know (have seen play) two, two way players in the Ivy leagues. One is now in the Cardinals bull pen; the other is steaming his way through the Yankee system. One played short; the other first. One's velo sat 90, the other sat 87 in college. Both were studs at the plate; average fielders. But, in the end your son has no real control of where he'll play.
(a) if he's good enough (b) he'll play anywhere the coach wants. So, the goal is to get good - very good in something - anything really.