Beyond all the advise that has been offered, there is more to it than just your son. A few years ago, I believe very few Ivy HCs believed in it and most not at all. From our 4 year experience in the "League" only Princeton had a consistent philosophy of allowing two-way players.
4 HCs within the Ivy have changed since my son hung up his cleats in 2014, so I think it is a fair question to ask the HC about his specific two-way philosophy. So, assuming you get through all the academic and athletic hurdles then you have to look at the two-way history of the program and then decide if this is something you really want to do keeping in mind: two-way travel baseball (at the highest levels) is not the same as two-way D1 Ivy baseball with the day in and day out throwing routines especially at SS.