Being Pooh sized myself, I would ask are your
Crocs new when you wear them to WDW? Or when you need to use them for alot of walking?
To really reap the benefits of Crocs they should NOT be broken in.
Yes you should wear them only a few times at the house to make sure they don't hurt your feet, but they should be new and not broken down.
As Crocs age they flatten out a bit and lose their support. The heavier you are the quicker this happens. (I get new Crocs every 6 mos and plan new ones a week before a WDW trip.
Also a running shoe is best as well. They are made for "high" or hard impact on your feet as you run. If you are heavier this helps in taking the brunt of the impact of just walking. (again, I have bad feet and this helps tremendously).
So what I do is start out in my running shoes with moisture resistant socks, by mid day or evening I switch to my Crocs and finish the day......works like a charm!!
Have a wonderful trip!!!