Hi, I just got back from a trip to Hawaii and we were in both Oahu and Maui. We only spent two nights in Waikiki and as far as we were concerned that was enough. The rest of the time, we were in Maui (7 nites) and I could have easily spent another 7 nights there! We did a Pearl Harbor and Honolulu city tour in half a day. Working in NYC, visiting Honolulu was like visiting a big city like NY, with palm trees.
While in Maui, do not miss Mount Haleakala with a bike ride down (38 miles) from the summit. It is a real rush and really very safe.

Have a great time...I wish I was going back.

Brian