Sorry, at age 5, I would be ditching the stroller entirely, and having the child walk. Certainly, I wouldn't be looking to spend a couple hundred dollars on one to last a few more years!
What we found helpful was to do "Disney conditioning" for a few months prior to vacation. We took our kids on walks--we went to the local HS and did the track. My younger DD could walk 3 miles when she was 3yo. Obviously, we worked up to that, but it was very easy. And at 3, she still used a stroller for Epcot (but nothing else).
We go to WDW again next summer, and our youngest will be 5. We are looking forward to having a stroller-free trip. It's amazing how much time, money, and space they take up!
You are seriously NOT doing your child any favors by pushing her around all day. Frankly, I'm stunned that you don't already encourage walking. No kindergartener I know wants to ride in a stroller--they're for babies.