Nice Aunt,
Everything Pontac says here is correct and spot on and I just want to add a few things. If this is her last cruise I would recommend looking at it through a different lens. Don't look at it through the usual cost analysis where every aspect of the cruise line's offering is examined for value. Go for the overall experience and splurge. Tauck and Uniworld have over the top gorgeous ships and great overall service. She will be pampered and doted on by the staff all while in a pretty luxurious setting. Any of the excursions, kayaking included, can most likely be arranged simply by stopping by the cruise manager's desk and asking. You might have to pay extra, but who care! Its her last trip.
We did exactly what you are doing for my father in law this summer. He is almost 90 and we took him on what is likely his last trip. The guy is notoriously cheap and will grind a penny out of any situation. We took him a small/mid size luxury cruise to the Fjords in a great cabin, he flew business class (first time in his life), ordered fine whiskeys and champagnes that were not on the AI list, ate at all the specialty restaurants etc. No restrictions and pure indulgence. 15 years ago he would have been griping about costs and how we could have gotten a better deal if he had done X or Y instead of what we did.
He had a ear to ear smile the entire time and couldn't stop talking about it when he got back. It was very special to us all and no one complained about the extra few bucks we wasted/spent. We removed, to an extent, the cost consideration, and just went for it. Best investment we ever made.