As Carol said, you need to check in first. You'll get the required resort ID regardless if your room is ready or not.
As a guest at the BVC, you'll have access to the health club where you'll find changing rooms and showers. I'm fairly certain that lockers are there as well, but I'd need to verify that before stating it as a certainty.
If not, you can always check a bag with the rest of your belongings once you've changed and no longer need it.