I'm kind of in the same boat (pun intended lol) I'll be traveling with my mother on Jan.30th. She's did this exact cruise last winter, and she's older, so I expect to be on shore by myself more often then not. There's a lot that I'd like to see on Oahu, but I'm leaning toward a simple visit to the botanical garden, and a makeshift tour using the hop on, hop off, buses. I'm the type of person who is content with just seeing hula dancers, instead of attending a luau so, if it's possible, I'll just stroll around some of the resorts and see what I find.
I'm still unsure about the other islands. I lean toward seeing nature, so hopefully there's some convenient options that aren't too expensive, and won't worry me about the timing of getting back on board. The Oahu stop is overnight, so timing isn't an issue there, but in general, the things that have piqued my interest seem to be quite a distance by car. I'm almost too safe when it comes to timing on shore lol