I have visited Oahu, Maui, Kauai and the big island. As far as I am concerned the must sees are: Oahu - Pearl Harbor and Hanauma Bay if you are in to snorkeling. The Polynesian Cultural Center is fabulous also but I do not think there is time unless you are up to it the first day. I do not know where you are flying from but we are not flying in until the 27th and with the time difference probably will be pretty worthless that day :) On Maui I highly recommend the road to Hana (600 curves and 54 one lane bridges) with the some of the most beautiful sites you will ever see. I also recommend a visit to Haleakala volcano. On Kauai I recommend the Waimea canyon. On the big island I recommend volcano national park.
Three of us are from Virginia and three are from Maryland . We are sooo excited - only 72 more days :)