It's not a big deal to get a cab. It'll probably be more expensive than renting a car (especially given that you usually get a price break for weekly rentals), and it is a really easy drive, but I have to admit that when we arrived in Waikiki at 8pm one year, we were pretty delirious by the time we collapsed into bed.
It's also a shame to spend a few hundred bucks a night on a hotel room when all you're going to do is sleep in the room and not enjoy the resort.