Aloha, Linda!
I'm so glad that you'll be visiting my island home of O'ahu very soon. You'll be sailing with Captain Mickey in such a short while -- and you'll be enjoying the spirit of aloha sooner than you know it.
There are various
Port Adventures offered and you can actually choose and filter your search depending on your interests and activity level. For O'ahu, I would recommend checking out the USS Arizona Memorial at Pearl Harbor. It is a leisurely boat ride and a short stroll inside the memorial. They also have beautiful grounds to stroll in for more pictures. If you are staying on pre-cruise hotel nights on O'ahu, you can check out other activities around the island - there are lots!
In Maui, you can enjoy the Lahaina Luau for an awesome Hawaiian feast in the evening, Linda. Yummm! Kauai (the Garden Isle), will be green and lush and mellow activities. There are are plantation tours where you can ride a train and sight see. Hilo on the Big Island, offers a Helicopter tour of Kilauea volcano.
At each port or tourist activity, feel free to check if there are wheelchairs available for your use, should you feel the need for one. The tour guides will usually show you an alternate path to get you the most out of your excursion, without having to deal with the pain on your knees.
I hope this helps, Linda. Please do let us know if you have any additional questions before you leave for your magical vacation!
~ Dolly