Laura:
Whether you were vacationing for 12.5 days instead of 2.5 days, you'd still not be able to do everything at Disney World. Go into your vacation with a solid plan of hitting the highlights, and you won't have any regrets nor feel rushed.
Spending an entire day at the Magic Kingdom is spot on. You can certainly hit the "must-dos" within a day. Visiting Epcot for a half day is fine, just go into your time there with the understanding that you can do either Future World or World Showcase but not both. With children, your time should be spent optimizing Future World, in my opinion. As much as you may want to dine at one of the great restaurants in the park, with such limited time, I would suggest that you eat at Sunshine Season's in The Land Pavilion or if you must venture into the World Showcase, eat a late dinner in France's pavilion for a "taste" without walking too far.
I don't know that I can rubber stamp spending your other full day at Animal Kingdom versus
Disney's Hollywood Studios. AK does not have a night-time "spectacular" and it closes earlier than the other parks. Additionally, for many children, the Disney characters they know are from Pixar movies like Woody in Toy Story and are the mainstay of DHS and shouldn't be missed. However, if your children are animal lovers and enjoy musicals, Animal Kingdom would be a fine choice, especially if you are planning a character meal in the evening at one of the Deluxe Resorts. I would only suggest that before you rule out DHS, that you make sure to compare the attractions in both parks.
Wishing y'all a magical vacation!
Whitney