We rented a full size car from Hertz (or at least what they consider full size, it was a Nissan Altima) for 8 days for less than $200. You can't do that in Orlando. But, if you're not
DVC (I assume you are) the parking at Aulani is $35/day. Ouch. Hertz, and many other companies, actually lower their prices as the booking date gets closer (for some locations). We booked and cancelled, then re-booked and cancelled again, until the we got the best price just a few days before showing up. Just keep checking the rates after your reserve on-line.
You can rent the car on site at Aulani, but that still leaves you without travel to and from the airport, and it might be cheaper just to rent all week, plus having the car was very helpfull to escape the tractor-beam of tourist price gouging. You need to get at least 4 miles away before you see anything that resembles mainland prices. And even then, it's still more than home. But at Aulani, forget it. 2 resturants, that's it. One costs $43 per person for a buffet, the other is fine dining starting at $50 per plate. They have quick service starting at $12 for a burger, and some other local flavors. Other than that it's a hot pocket at the store, or walk across the street to a little plaza with a market, and a mexican place, both still over-priced.