I had to exclusively pump (EP) for DD for various reasons, and we took her to Disney during that time. I wrote out a bunch of tips on pumping at WDW when I got back. Here are links to my story and top tips for pumping at WDW:
My experience EPing @ WDW
My top tips for EPing at WDW
Since I had a pump that could work on battery power (Ameda Purely Yours), I didn't need to be tied down to the baby care centers or any places with power outlets. It was incredibly helpful to have that freedom. There's still a lot of good tips in there, though, if your pump won't function on batteries and you do need to go to the baby care centers
The most important tip, though I know it wasn't what you were asking about, stay hydrated! Drink more water than you usually do! I didn't do this, and it affected my supply and took me a bit to recover from. Counter Service restaurants will give you water for free...drink as much as you can stand to drink