I suggest renting a vehicle at the airport - cheaper than other places. That'll give you the chance to drive around and see the island. Be careful of the North Coast, because it can be extremely crowded during surfing season. But there are some amazing roadside shrimp restaurants up there that are awesome! They have their own shrimp ponds in the back, so your shrimp were alive 5 minutes before you eat them. Can't get any fresher than that!!
You can also pre-book reservations at Pearl Harbor, which is a must for those of us who are ex-Navy.