Which Park Hyatt?

Award night in NYC's double beds (hard to come by) can accommodate 4, while in Milan, award room is only available for up to 2. Nevertheless, since you are already cleared into a suite, I would just call WoH and see if they can change your booking to 3 adults. My money is on they will look at the suite's occupancy rate and adjust this for you. If this is successful and we are talking about properties with 2 max occupancy award (excluding AI as Matt pointed out), you might just find a backdoor for the 3rd or even 4th adult using a suite upgrade cert.