Hi,
Is your son not on Resident visa at the moment (i.e the same visa which you have)?? Why does he need PR to move to next year in university?? For your information, all the offices like banks and universities etc, our SMC resident visa is equal to PR visa for administrative things (as they dont really differentiate between RV and PRV as both allow us to live in NZ indefinitely).
Unless your son is on student visa and not on Resident visa, I dont think there is any need to worry. Your RV should be fine.