Have A Magical Trip!
I concur with popsicletrees : pick (at least) one day to visit EPCOT and make sure you get there as soon as you can in the morning. Walk in and go straight to Soarin’ to get a FastPass; it is a must see!
Basically, whatever park you choose (and I agree with the one-park-per-day mandate) head straight to the main attraction that you want to ride and pick up a FastPass; then, you can dawdle and poke around to your heart's content. My recommendations would be: Expedition Everest at Animal Kingdom; Splash Mountain or the Haunted Mansion at MK (although I think HM is down for refurbishment?); and... drumroll, please... my ultimate favorite... the Tower of Terror at MGM!
Don’t forget to watch Wishes at least once while standing on Main Street. It’s just not the same if you’re off-site or watching from anywhere else. It will give you goosebumps.
Whatever you do, wherever you go, just make sure you take plenty of time to wander around and look at everything. Some of my favorite things about DW are the least frequented, or do not even qualify as official attractions: the Tomorrowland Transit Authority; the Shootin’ Arcade in Frontierland; wandering down Main Street and reading all the names above the stores (did you know Walt’s is the only name that faces the Castle?); walking through Cinderella Castle and admiring the stained glass inside; looking at Lady and the Tramp’s initials in the concrete outside of Tony's Restaurant; reading all the tombstones outside the Haunted Mansion; etc. Also, I am a hotel fanatic, so I love just hopping on the tram and meandering through all the hotels, but that’s kind of a personal thing. (If you’re into that, I highly recommend the Swan/Dolphin, Animal Kingdom Lodge and Grand Floridian.)
If you decide to go to Epcot, make sure you visit Germany - they have an absolutely phenomenal RGB train setup that is a must-see. Also, although every “country” is delightful, France has a fabulous little mini-street with a gorgeous fountain, and Great Britain also has a mini-street with a stage at the end that houses a fantastic Beatles cover band (make sure you check the schedule for performance times). There’s nothing like standing next to a red phone booth listening to Sgt. Pepper tracks while the sun sets and people dance in the “street.”
But the single greatest thing about DW is when you enter the Magic Kingdom, walk to the center of Main Street and BAM, the majesty that is Cinderella Castle just takes your breath away. Every time I visit, that moment turns me into Tom Hanks from the movie Big - I instantaneously morph from a 24-year-old law student and chronic pessimist (my family calls me “Eeyore” despite my distain for Pooh) into a 10-year-old who adores Lady and the Tramp and Ratatouille and is absolutely not too old to hop up and down with delight upon glimpsing Chip or Dale. For a few precious days, reality is suspended, dreams really can come true, and anything is possible.
Wow, sorry for the extended post. I guess the long and short of it all is: have a blast, and forget that anything beyond the bounds of Disney's property even exists. You’re in Walt’s world now.