I depends on how you like them to feel. I wear a 7 or 7 1/2, depending on the style of shoe, and I get 7's in Cayman, Mary Jane, and Cleo style
Crocs. I wear a S (6/7) in the Beach style. I like them to feel less "sloppy" and more snug on my feet. They do tend to stretch out a bit after you wear them a while- they conform to your foot.
Don't know about the Disney ones, but the regular Jibbitz do fit in Airwalks.