Thanks for the info and opinions everyone!
What things would you recommend? We are a family with 4 children traveling with us. Pearl Harbor? Dole Plantation?
Do you recommend renting a car for the ride to the resort so you can stop at Target?
Where is the best place for souvioners?
Tons of questions! lol
We've rented a car both times on Oahu. The secret is to keep checking rental rates constantly. We were consistently seeing $500/9 days and all of a sudden it dropped to $220. I grabbed it and it was back to $500 the next day. Also, unlike the Waikiki Beach area, Aulani is not close to much. There are a couple of restaurants you can walk to, and a convenience store, but not much else. The Target is only a couple of miles, but too far to walk.
The other thing about a car is the ability to do multiple free or cheap excursions. For example, we enjoyed the Manoa Falls hike and it cost us $5 for our family to park. If you take a tour to Manoa Falls it's about $40 a person. Same hike, but the transportation costs a bunch to get there. Diamond Head is another example. Super cheap if you drive, but to do the tour with transportation it's much more. If you can get a reasonable rental I'd definately go that route.
As another poster noted, you can definately spend the entire time at Aulani. The resort is incredible and you won't have trouble finding things to do. However, I feel you are missing too much of Hawaii if you do that. There's so much to see that we packed both vacations with events and could have still spent more time.
A couple of favorites:
Manoa Falls - super cheap, lush vegetation, a walk through the rain forest, ending at a waterfall that can be a trickle or fantastic depending on how much it's rained in the mountains.
Hanomoua(sp?) Bay -World famous snorkeling for $7/person plus renting the equipment for about $5.
Tantalus Drive/Round Top Drive - a drive to the top of the mountain and back down with sweeping views of much of the Eastern side of the island.
Koko Crater hike - if you are athletic this was one of our favorite things. A walk nearly straight up the side of a crater on an old transport rail. Free if you don't count the sweat and tears you'll lose on the way up.
Diamond Head - the classic Oahu hike, cheap to park and no fee to do the hike.
Pearl Harbor, we especially liked the Battleship and the Bowfin sub, but the entire exhibit is worth seeing and the costs are reasonable.
We've also done other paid items such as the Shark Encounter, Kuoloua Ranch, Snorkel excursion, swim with Dolphins, surf lessons with Hawaiian Fire, PCC. Let me know if you have specific questions.