Glad to hear you are heading to our 51st state. The best advice I can give is to do a car rental on the islands. You may have to take a short cab ride to the rental areas on Kauai but IIRC the rest of the islands have car rental areas near where you dock or tender.
The road to Hana is beautiful but it is a full days journey. A helicopter tour on Kauai and a drive up to Waimea Canyon are great to do.
On the big island you really need to visit Volcanoes National Park and see the lava flows and other sights.
Have a great time, grab a guide book to determine what you want to see and do the car rental.