Someone on another thread called this sort of move "future - proofing" and I think it is a very good way of looking at the moves we need to make as we get older. It was certainly on our minds when we moved here - yes, to be near the sea, yes, to have a calmer, quieter life, but also to be near DD.
Although we are not in a great deal of need right now (apart from me and my joint replacements) we have a lovely feeling of security with DD and family nearby. She and I also thoroughly enjoy doing all the things we have missed over the years - impromptu shopping, lunches and so on. And we run the DGC around, take /took (they are now 18 and 16) to the dentist, doctor hairdresser. I love texting DD and saying I am going to Waitrose, does she need anything. Lovely!
You do have health issues, and they are not going to go away. We didn't downsize much, but the location is convenient for all services.
Sorry, I have gone on a bit, but it was the best thing we ever did. Go for it, mishap!