Like the last answers said, it will be busy, and no matter how high of expectations you have, WDW will exceed them! I agree with everything the previous answers said, so take that advice in addition to mine. Here's some of my favorite things to do and some tips and hotels.
I would start by going to disneyworld.com and allears.net! This year they are running limited time magic. They announce them as they occur. Check limitedtimemagic.com on Fridays to see that week's announcement! The following are my favorite rides, shows, and more. Some of them are kind of aimed towards kids (like Buzz), but are fun for all ages. If you are "too cool" though, don't do it, just know they are great fun. Any ways, here you go:
Magic Kingdom: Haunted Mansion, Pirates of the Caribbean, Wishes, Main Street Electrical Parade, Celebrate the Magic, Big Thunder Mountain, Buzz Light Year, Small World (Music's annoying, but it's a classic), Jungle Cruise, Mad T Party, Philhar Magic, Monster's Inc Laugh Floor, Peter Pan, Under The Sea, and Carousel of Progress.
EPCOT: Ellen's Energy Adventure, Gran Fiesta Tour, Journey Into Imagination, Maelstrom, SOARIN, The Seas, SpaceShip Earth, Test Track, and Illuminations. (I don't know how much you like educational shows so I left them out.) Additionally there are lots of entertainers and things to see.
Hollywood Studios: Great Movie Ride, Legend of Captain Jack Sparrow, Muppet Vision 3D, Rock 'N Roller Coaster (ONLY IF YOU LIKE BIG THRILL), Star Tours, Backlot Tour, Toy Story Mania, Twilight Zone Tower Of Terror (Thrill, but more show than thrill), Beauty and the Beast, Fantasmic, Indiana Jones Epic Stunt Spectacular, Lights Motors Actions, and Voyage of the Little Mermaid. Tons of shows, so beyond this, just kinda do what looks cool. These are the must dos though!
Animal Kingdom: Conservation Station, Dinosaur, Expedition Everest, It's Tough to Be A Bug, Kali River Rapids (You will get wet), Kilimanjaro Safaris, Festival of the Lion King, Finding Nemo, Flights of Wonder, There are endless trails and paths to walk through and see animals, so I'll let you decide on that.
As far as dining goes, for most sit down restaurants you will need a reservation. You will have a good time no matter what though. Just go with a smile. :-) There are also tons of character meet and greets through out the park. Look at the calendar on Disneyworld.com to plan what days you will be in what park to make sure you can see the shows, as they don't all run every night. Also, Disney Quest (located in Downtown Disney) is a five story arcade that has awesome simulators, new video games, and the classics. There are two water parks, Typhoon Lagoon and Blizzard Beach. Blizzard Beach offers a more thrilling experience, while Typhoon Lagoon is better for families. All three require extra admission. (or if you have "fun and more" on your tickets, that is what it's for.). Disney World has two mini golf areas, also requiring extra admission (or "fun and more"), that have a touch of Disney Magic. As far as hotels go I would recommend the following;
Value: Pop Century, great fun and you can walk across the bridge to the newest resort, Art Of Animation.
Moderate: Port Orleans French Quarter, you can walk to River Side. It is the smallest Disney resort, which is good as you will walk a ton. You can take a boat to Downtown Disney and back.
Deluxe: Beach Club, sand bottom pool and lazy river. You can walk to Epcot or Hollywood Studios. Additionally, you can walk to Yacht Club, Board Walk, Swan, and Dolphin. Five hotels for the price of one! You do need a valid Beach Club room key to access the pool though.
Also, things like Fantasmic, everyone reads the same tip: the second show is less crowded. Because everybody reads that though, it's not so true anymore. Take tips like that at your own risk! Make sure that you have at least one day for swimming and relaxing at the hotel. Get Fast Passes for the newest rides, as they are usually the longest lines. You will be there as they are updating to the new MyMagic+ system, meaning that rather than having a ticket, a hotel room key, fast passes, gift/credit cards, you will just wear a wrist band. The wristband will count as your park admission, your hotel key card, credit card (optional), and your FastPass. The FastPass system will be upgraded to FastPass+, so you decide online which attractions you want a fastpass for on which days at what time. You can then edit your decisions in the park, online, or on a mobile device. Like I said earlier, you will have a good time no matter what, and Disney World will exceed ANY expectations you have, no matter how high they are. Benefits of a Disney Resort are early admission to the parks, complimentary transportation to the parks, and you never truly leave the Disney Magic!
Hope I helped,
- Andrew