Bette, I don't know how restricted Marty is but if he can manage it, Japan is really worth seeing.
Don't write off Tokyo as it has a lot to offer - beautiful Japanese Gardens and the fish market is an experience not to miss. I took full day trips from Tokyo which could be an idea as that way you're not packing up each night. The food in Tokyo is fantastic.
If you decide you do want to go, let me know and I'll ask Michael for suggestions. He organised our trip to Kyoto and Hiroshema. There was one tour I went on (can't remember which one) but it stopped at a type of health resort in the countryside and let people off and then another tour picked them a couple of days later.
I know it can't compete with a world cruise and obviously it's no good if Marty can't get around at all but I really enjoyed Japan and wished I could have seen more.