At Disney in CA there may be less walking than WDW, but it's always good to be prepared. I have been on a fitness journey since March, so everything has changed from "A theme park means a place to eat," to "A theme park means a place to walk and get more exercise". Comfy shoes are important, but also shoes that are for walking are just as important. My three big tips are;
* Never, ever wear brand new shoes into the park. Do your best to break them in for a week or so before you go. New shoes always need the break in period, and you don't want blister problems in the park.
* Something else to think about if you go to WDW when its very hot and humid, that you feet swell, so its better to take some extra pairs of thin socks, to compensate when you feet get a little too large for your shoes. Believe me, I know the pain of swollen feet in shoes that used to fit fine. We finally had to rent a car and go off property so I could get bigger shoes.
* A bit off topic tip here. If you aren't used to walking a whole bunch, it would be best to start walking a quarter mile, then a half mile, then work up to a mile the week before you go. Being sore is tough to work through, so if you can get used to extra exercise before you get to the park, you will have more fun.
Ok, that's all the blabbering from me.