Fortunately, my father is still doing well in his 80's, but I expect to face a similar situation at some time. There are hundreds, if not thousands, of slides, most of them still in very good condition. He has forgotten the location and situations of a few or them. Most of them are of little historical interest.
In general, historical photos of famous places are usually useless, there are just so many of them. Old photos from smaller communities may be of interest to local libraries and historical societies. And even them, a photograph of a hardware store may be of more interest than a photograph of a monument.
I realize that 99% of the photographs I have taken is of little interest to anyone besides me. I look at some of my old travel slides from the early 80's, but their value is primarily that I was there ... and I took the picture.
As for old photos, when I get a chance I post them on the internet in case someone has an interest in them. I save all the slides, knowing that most will be thrown away long before the Kodachromes go bad.