go to My DisneyExperience, the Annual Pass will give you flexibility to switch from park to park, however the 3 day options between Hollywood Studios, EPCOT and Animal Kingdom will cost you more or less the same as the basic annual pass but there is not enough time to go to every attraction within those 3 days because of the wait times.
We got our online via Disney.
Right now there are deals to be had... Check the web site for a full listing.
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