Banjoman, have a wonderful time! My suggestions for the 2 days after your cruise - you'll have to pick & choose, but there are 3 major things to do on Oahu that I have enjoyed and would recommend: first, for relaxation, just enjoy Waikiki Beach. Stroll along it, hang out on it, etc. Second, visit Pearl Harbor and take a tour there - preferably one that includes a visit to both the Arizona Memorial and the USS Missouri. Very inspiring, touching, informative - and important for everyone to see. Third, visit the Polynesian Cultural Center for a great overview of the major South Pacific cultures, taught in a fun way. It's an all-day expedition, and will require either being part of an official tour, or renting a car to get there. (FYI, it's not open Sundays.)
Whatever you choose, enjoy the Aloha spirit!