Old thread, but since it's being advertised on the bottom of the DIS page, and I have first-hand experience, I thought I'd share.
First, the bay where Aulani is placed, is part of a homeowners association area, not a public beach. Aulani enforces the homeowners organization rules of no private use of surf boards, boogie boards, SUPs, and the like- they must be rented there at the beach. This controls amount of usage of such items, and covers liability.
Beside Aulani is a public access parking lot- limited spaces, no fee. Locals, or anyone with ability to grab these spaces, may use the parking to access the bay, and do so for free. They are able to play on the beach, rent the equipment, and, if no one is securing the gate that leads up to the Aulani pool, they are able to go onto Aulani's property. They may also eat there too. Usage of the slides, snoring area, and group activities such as at the community center and Aunties is supposed to require proof of staying on site, but not always enforced.
We were happy to find some locals to play with, on the beach- real nice kids and family. Let it be known, though, that public persons may be amongst on site guests.