Hi Cherisse, welcome to Cruise-Chat. Congratulations on your up-coming cruise! Here are a few suggestions, but there are a ton more.
Oahu: The Arizona, Diamond Head, Haunama Bay, Toilet Bowl, North Shore, and the Punch Bowl.
Hawaii: The Emerald Beach, The Black Beach, Mauna Loa.
Kauai: Old Lihue Plantation, Kipu Falls,or do a snorkel tour or a whale/dolphin tour.
I doubt you'll have enough time to do a whole lot on any of the islands, so I highly suggest researching each destination and find what you really want to do. There are so many beautiful water falls and forests and lakes and beaches. It's truly an amazing state! Best wishes!