I went a couple of years ago, From what I remember there is A LOT of walking involved to get to the sights and when I was there it was drops at intersections. People are rowdy and not really considerate but, then, I was healthy. I agree that only you can make the decision as to whether you think you need a chair or not but I think it will be hard getting around with a walker and the sheer size and distance of the place. But it depends what you are going to do; do you have a plan as to what you are going to see? Maybe go on google and search distance between the places you are going? If you think you’d be alright with a walker plan days so that the attractions on that day are near each other? But I’d seriously consider getting a scooter, just because of the size of the place and the rowdy crowds. There is also a lot of roads that need crossing, consider how fast you are crossing as from what I remember the lights don’t change for long.
I don’t want to be a downer for you, only you can make this decision, I just thought I’d be honest for you.
Take care, Dante.