Hi, so Aulani is in an area that is a private resort community. It is made up of a few hotels, a golf course, and the surrounding condos and houses of that community with a very small shopping area. The only bike rental that I have seen online is from the Ko'olina community area. IDK if they are still renting at this time, you would probably have to contact them. To get an idea of the area, I recommend Google maps. That was you can see that area and what is available. If you have not rented your car yet, I would do so ASAP. You will need it to go anywhere since Aulani is in a isolated area of the Island.