Actually, despite the eyesight and other issues, from what I have seen, older people, especially older women love tablets. Even some that type enough I wondered how they could prefer them. Not sure I get it, but I have seen that to be the case in several instances, and most of them had/have a desktop or laptop. So they aren't people new to computers.
I think less dexterity is needed to poke the screen in your hands than moving a mouse, along with the OS being set up for touch screen interaction. Those who get comfortable dictating longer emails and notes do seem to need nothing else. Their other computers seem to sit idle.
If the person in mind needs only a desktop device a chromebook might be the better choice. But I have also seen older folks once they have the portable tablet, make much more use of it all over the house when they didn't spend as much time actually computing at a desktop. So despite lots of things saying a tablet is under-powered and not best to interface with for all purposes, something about it seems to get along with older people better.