The best part about Disney is that you can be in almost any field and find employment with them. Pick a major based on what you want, and you'll find it relates to working with Disney somehow.
I think Business is a good major, and I bet many Disney employees have studied that. Some other common ones for a theme park environment are Culinary, Hospitality, and Communications. For corporate, maybe Animation, Illustration, Education, Accounting, Marketing, etc. A good way to explore is to run a job search and see what the qualifications for each opening are. Find some that appeal to you and start learning the skills needed to work in those roles.