An order of fries from Casey's can be dressed up with melted cheese. Also, corn dog nuggets are awesome there too. They have something called "Ball Park Nachos" that I assume is a container of nacho chips that you drench in hot cheese from the fixin's bar - that could be easily shared by the whole family. I think it was under $10.
I like to get a caramel sundae from Storybook Treats in Fantasyland. It's a huge soft serve vanilla (can be swirl or chocolate) with caramel, whip cream and a cherry for under $4. Eat fast, though - it melts!
At Sleepy Hollow, I like to get a Funnel cake. I haven't tried the chicken waffle sammich yet, though they look really good.
Pretzels are filling, (since it's bread). How about a bowl of soup or baked potato in Liberty Square?
As others have mentioned, the popcorn is better than crack! Main Street Bakery has cookies, cakes, pastries, MUTANT cinnamon rolls, as well as a few cold sandwiches.
Happy eating! We'll be there for Leap Day, so I'm starting to think about what I want while I am there, too!