You can get stuffed character toys at all kinds of places in all kinds of outfits. Frankly, you can't walk 50 feet in the MK without running into a place that sells stuffed toys! You'll find them in the resort gift shops, all the parks, Downtown Disney...everywhere. There are some designs you will find in all the stores, and some that are specific to only a few locations.
The smallest "beanie baby" sized figures are $8, and you can get them dressed for many of the attractions. My kids picked up a bunch of different $8 figures last week - scuba Mickey at The Living Seas, astronaut Mickey at Mission:Space, "bellhop" Goofy at Tower of Terror, Indiana Jones Pooh in Adventureland, Philharmagic Donald, and many more. (My wife found that buying them one of these every day really cut down on the "I want this...no I want that" dawdling at the gift shops. Yes, it was a bribe, but it was a real time saver!)
There are also some larger 9-12" dolls for $12, and my daughter got a large Minnie (probably 18") Minnie at the Fantasia shop in the CR for $22 or so.
I'd wait for the trip. A toy that reminds them of what they liked best about WDW will be a favorite for a long time.