We used Hawaii Cruise Excursions and Tours Guide for Tours on the Islands of Oahu, Maui Big Island and Kauai Hawaii
for our cruise in January 2011 and would use them again. Good selection of tours and some cheap prices. I don't know what your itinerary is, but for the Big Island, you have to go to the volcanoes. We took this tour and it was great. Our cruise ships tour was on buses, but this tour was in a van with our own guide. Kai was so friendly and we had a great day. I defnitely recommend going on a smaller tour for the volcanoes. For Oahu, you need to see the major sites, and go to a beach. There are beautiful beaches on Oahu. Waimea Bay Beach is gorgous and so is Kailua Beach. Of course Waikiki is great, but there are some more beautful beaches that are less crowded. Maui is the Road to Hana or Molokini crater for snorkeling. Depends on what you are into. We went to Molokini crater as we are divers and it was on my bucket list. Kauai is beautiful, we did a helicopter flight. It was an hour and a bit expensive, but it we wanted to do one helicopter flight. We used Kauai Helicopter Tours - Service with a Smile & Impeccable Safety Record | Safari Helicopters
and they were great. Have a great vacation! We are about to start planning our winter cruise, haven't decided where yet, but might go back to Hawaii!