I really feel for you Summerof75 - (I've been there, done that ... with my own parents) but I agree with Tanith. It is THEIR decision, and all you can do is support them best you can. If they want to stay in their own home, then it is again, their choice. So getting more help for them, and getting a shower suitable for disabled and a loo downstairs would be great.
I've known friends who bought a huge house with their parents to share- and in every instance it turned out to be a disaster all round, as the needs of different generations differ so much. And also known friends who up-rooted their parents to come and live near them- and it just didn't work out, as they missed their friends and familiar surroundings too much.
I intend to listen to my children and take on board their advice and accept their help, when the time comes- as long as I feel I am in charge of my own destiny. I intend to get help here with the big house and garden as and when, and have no intention of going to live in a 1 bed bungalow or an OAP home- and would really resent it if I was pushed in that direction against my will.
Hope you find a way to feel re-assured and yet allow them to make their own decisions.