Have been to Hawaii a couple of times, but not on a cruise. Akaka Falls is incredible; you'll love it. Luaus are also great fun, not to be missed. Kauai is exquisite. Hanalei and Poipu were my favorite places there.
Lots of options for the Honolulu area. A few of our favorites:
1) Pearl Harbor, the Bowfin, and The Missouri--any or all are wonderful tours.
2) Hanauma Bay--If you have the option of going snorkeling at Hanauma Bay, I'd highly recommend it. Hanauma's beach is beautiful, and the snorkeling simply can't be beat. You can easily go through a couple of underwater cameras there in no time--there is soooo much to see underwater. You could easily spend an entire day there, but even a couple of hours would be great.
3) A tour that includes a drive at least part way around the island, particularly one that takes you to Oahu's North Shore, where you can see the incredible pipeline surf.
On the Big Island (Hawaii), would highly recommend touring Volcanos National Park if its an option for you. Fascinating place!
The only "adventure" in Hawaii that I definitely would not do again was a rainforest/waterfall hike--not a good experience at all. But then again, I booked independently. If you're booking through a cruiseline, you may have a very different experience.