I don't know how qualified I am to put my two cents in (I don't have kids yet and I was educated in public/parochial schools), but I do have a few ideas to share:
History/Social Studies:
American life/southern California in the 1950s
the history of
Disneyland itself and its long-gone attractions.
Science:
The rides are a perfect example of physics and engineering in action! You could gather info about how roller coasters/theme park rides are designed and built. The Travel Channel shows programs about the work of Imagineers all the time, so keep your eyes peeled for stuff you might want to record.
Math:
How to budget for a vacation (If they're younger, money management for just souvenir/treats is probably sufficient)
Trip scheduling and time management
Miscellaneous distance calculations (i.e. miles between home and DL, how many steps it takes to get from Frontierland to Fantasyland, etc.)
Art:
(My favorite subject and what I studied in college!)
There are great examples of art all over the park, like the posters in the entrance tunnel and Red Rockett's Pizza Port. Have the kids compare, contrast, and analyze the graphic design trends of different eras, focusing on color, typography, and composition....which can easily segue into a connection to history. (i.e. Mary Blair and her contributions to the old Tomorrowland and Disney films.) There are a ton of books about Disney art and animation, so it probably won't be hard to find something that will spark a kid's interest.
Disney Animation Academy in DCA serves as a good introduction to animation.
I hope I helped!
