How nice to hear from you!
I personally prefer planning a trip and staying for a chosen number of days at each place of interest. On a cruise, I usually feel rushed. That said, I know Royal Caribbean has nicely accessible cruise ships and the ports of call can be checked out to be sure they are accessible. Before Covid, I was going to go on a Royal Caribbean mediterranean cruise that stopped at Rome, Napoli, Espezia (near Florence and MarseilleFrance, France). All of those parts I was told are wheelchair accessible and when I did research for excursions, there was lots to do. I know a cabin size of 188 ft.? for two people works for me. But I am the only one in a wheelchair.
I know there are many things to do in London that are wheelchair accessible. The UK in general is very good about wheelchair accessibility. I also know that Rome is nicely accessible although you can?t do some of the ruins in a wheelchair but you can get near to see the Colosseum, for example. I know less about Paris because when I went there, I was able to still walk. I hope this helps.