Hi Jennifer!
Welcome to the Disney Parks Moms Panel! I love picking up party and craft supplies at Walt Disney World Resort! There are so many fun ways to repurpose all kinds of Disney things. Sadly the Mr. Potato Head Pick-A-Part souvinEAR experience is no longer around. But I'm not out of ideas:
If your party is a Toy Story theme: Toy Story Land opened just a few months ago in Disney's Hollywood Studios, and there is another Buzz Lightyear themed attraction in Tomorrowland in Magic Kingdom Park. Definitely take a lot of great pictures of your family in front of the various artwork to use as decor. You'll also find lots of Toy Story toys all over Walt Disney World Resort, like a bucket of toy soldiers and a canister of little green aliens, both of which would make for cute decor and fun party favors. You could even get chocolate coins as Ham's piggy bank loot.
If the party is a general Disney theme, head for the
Coin Press Machines. These are also found all over Walt Disney World Resort, and every machine features three designs that usually represent the area where you are, like Spaceship Earth in Epcot. You could collect coins from all over the 'World and display them grouped by park.
I love the Mickey-shaped drinking straws which sometimes come in specialty drinks at dining locations like Casey's Corner in Magic Kingdom Park. I've purchased these straws by the dozen at a few different Disney Resort Hotel Quick-Service dining locations. At under a dollar a piece they are both fun and functional.
Park maps can be used as table cloths and for paper crafts. Stop by any Guest Relations location to get a 'Happy Birthday' celebration button so the birthday mouseketeer can celebrate in Disney Style. And if you ask nicely, I'm sure you could even acquire enough Mickey Mouse stickers for each guest.
See You Real Soon, Jennifer!
~Kristen