You check in at the valet stand, they will call concierge, if your room is ready you and your luggage is loaded and driven to Hawaii. If the room isn't ready, your luggage is tagged, stored, and you are driven to the concierge lounge to check in and become oriented to the building.
You will be welcome to take full advantage of the concierge service from your arrival time even if your room isn't ready. Further, if you have packed wisely and have your swimwear handy

you are able to change in the third floor restroom and may head to the pool until your room is ready. OR if you would rather hop to a park while you wait on your room to be ready, you can stow those essential items you didn't check at the valet stand at the back of the concierge check-in area.
We've had it both ways--room ready, room not, swimming while waiting, park hopping while waiting. . .it's all a matter of preference. Just be sure to grab a water, soda, and relax while checking in with an orange-guava juice refresher. We've arrived so early in the a.m. before that the kids cool their heels in the upstairs lounge munching breakfast while we check-in.
We also usually leave so late that we spend an entire day utilizing the lounge and hospitality of the concierge staff. It's great to have a changing place before your room is ready AND after you've left your room at trip's end.
Have a great time--we're looking forward to our return soon (but not soon enough).