I would check-in early so at least you can have your room request in and they can even go over what rooms will be available later since they will know who is checking out that day. You'll be given your room key cards and a number to call to see if your room is ready and room#. When the room is ready your key cards will be activated and you will be able to go directly to your room. Although at AKL they gave us a beeper and we went for drinks to wait about an hour or so for our room to be ready. They did the same at CBR a few yrs ago too - both times we were happy to hang out at the resort and wait.
After many many years of travelling all over the world the one thing I've learned is to always check in earlier rather than later, if possible. By 4 pm check-in will be pretty busy.
Or it's possible a room might be ready when you do check in - even one you'll really like. Never know what may happen!
Good luck!