I agree with everyone here, Target,
Walmart and Dollar Stores seem to have cute Disney stuff for cheap. There are both Target and Walmart not too far from Disney so if you have a cr they both have some cute and inexpensive Disney themed stuff. They won't say Walt Disney World on the stuff you find in the stores, but most say Florida.
You can also find some stuff at the outlets that is directly WDW merchandise but I don't think you want to give the kids shirts and stuff, and they don't really have many toys at the outlet.
In Target look for the tubes of glow bracelets. They are 15 for $1 and have little connectors to make a bracelet. Kids love them. They are so cheap that you can give them 2 or 3 and make necklaces and not break the bank. Other stores have these but they are cheapest in Target.
don't forget the autograph books. They have some cute journals at christmas Tree shop that would make great autograph books.
Also, you can buy a cute "passport" at Epcot for going around the country. I did this one year with my neice and nephew but they liked last years idea better.
I bought a small photo book for $1 at Michaels. It holds 120 photos (60 pages. I also bought 4X6 plain cards and used them for the autographs. I got tons of clipart and pasted the photo of the character onto the card and the character loved having their own card to sign.
I also went to each country in Epcot and had the CM write something on the card, like "Hi (name) welcome to Germany, have a great day. Don't forget to visit Dar Teddy Bear and try some bratwurst" I told them to write whatever they wanted about their country. I then had them stamp it with their Mickey stamp(every country has a Mickey head with a hat representing their country) I also took one of the cutout cardboard shapes that represented their country. DOn't forget to write the english translation of what the CM wrote on the back of the card or another card. If you can get a photo of your child with the CM for the book too after all they are giving you their autograph.
they have their autograph books on their desks and they look at them alot still.