You'll be able to check-in then, but don't expect to actually get into a room. Just leave your luggage with bell services and go off to one of the parks.
As far as room requests go, you should have specified them when you made your reservations rather than waiting for check-in. Call them now and have them added to your reservation. Typically, people request what is important to them, such as smoking/non-smoking, lower/upper floor, near/away from main building.