You sound very well prepared. The only thing that I might suggest that you didn't mention was an automatic litter box. You can get one for about $70 now and would be a good investment. My parents have one for their 3 cats and LOVE the convenience of it. You only have to dispose of the waste container and just add litter when needed. No real heavy lifting (large bags of litter - new or used). They are really happy with theirs. I have thought of getting one but my old man would probably not approve. And he knows how to make his opinion known. I can't even change the litter, the only one that he will use is the TidyCat MultiCat Formula. Stubborn old man.
You might do some research in your area about adoption. I would suggest that you be open to the possibility of adopting two. If you look around there are usually loads of middle age (3-7 years old) cats looking for new homes. Usually because their former owners have passed or moved into retirement homes. Sometimes there are pairs available. Just keep your options open. It is not as necessary to have a playmate around for the older cats. No like when they are kittens and REALLY need the company.
And as you look around, a lot of shelters and adoption groups waive the adoption fees for older people adopting middle or older cats. Look into it.