We are in the processing of sort of downsizing - we are moving from a large cottage with steep access and internal steps to a bungalow, which is not much smaller in terms of space, but is flat, flat, flat! - hooray! We too are moving just a short way - about 8 miles, so we are hoping to continue with many of our social activities. We are hoping that it will all go through for beginning of July.
It is the most sensible decision for us - nearer to family, on a bus route etc., and, like you, we hope that it will mean we can do more and will not be reliant on others as time goes by. We are 67 and 69 and everyone is telling us that we are doing it at the right time - before we get more decrepit - something we are quite good at!
Maybe the thing for you to do is to start just having a bit of a look round for property - on the net, the local paper etc. This is what we did in a vague way for several years, and saw nothing we fancied; then, all of a sudden, there was a bungalow that we felt we could be happy in that came up.
If you leave it too late, you might find the idea of a move too stressful and burdensome. And you may find that you need to move suddenly when things get too problematical and may find yourself with less choice - you have to get out and you have to take whatever happens to be available at that moment. We are hoping that we have chosen the best window of opportunity - we are fit enough to make the move and we have been able to look around and make a choice, taking our time.
I do hope that you manage to find the right property for you.