I did NCL Wind around the islands, with a side trip to Fanning Island that took four at sea days to get back and forth. I loved it.
Our stops were at Hilo, Hawaii, where we rented a car from National and drve to Volcanos National Park, drove around there and saw the sights there. Then we came back and went to Island Candies (I think that was the name). Very easy to do. We easily could have seen more of the island, including the beaches, but it was rainy, so we didn't.
In Maui, we again rented from National, which was not as convenient to get to as on Hilo, but still relatively easy. We drove to the Maui Ocean Center, and then had time to tour the downtown area.
In Kauai. we rented a car and drove to Waimea Canyon (awesome sight); then stopped at some of the beach areas, and towns on our way back. We tried to get on the ship's tour that visited where movies/TV shows had been filmed but that excursion was filled and had a very long waiting list.
In Kona, we just walked around the town (it was our last stop, and I think we were touristed out).
We loved our cruise, and thought it gave us a wonderful overview of Hawaii. We also stayed a few days afterward on Oahu, so we got to see Pearl Harbor and the Polynesian Cultural Center. There were a good number of activities onboard--we liked the daily trivia contests. There were hula lessons, and craft lessons. I don't know what would be offered on the 7 night cruises since they are so port intensive.
You may want to check out cruisecritic.com--lots of people over there have done the Hawaiian trip.