About two months before, I started doing 2 miles a day at 4 mph on our treadmill at home, which took 30 minutes. Then I started staying on 45 minutes for 3 miles once it got a little closer to our trip, and would sometimes stay on for an hour (4 miles) if I had the time.
Now, that doesn't really compare with walking all day at the parks. But it definitely helped my feet get used to walking every day!
I remember seeing a weight loss site where Lord of the Rings fans would "walk around Middle Earth". Like, after they walked so many miles working out, they would "be" at a certain place in Middle Earth and stuff. I thought it would be fun to "walk to the Magic Kingdom" by our trip next May. That's about 550 miles, so I better get going!