If this is going to be your first, and possibly only trip, my main "must do" would be to plan. wdwinfo.com and easywdw.com are fabulous resources to read about the parks/rides/resorts/restaurants, you have plenty of time to figure out what sounds good to you and what exactly you want to do.
Without nothing else to go on, if I wanted to see as much as possible on a commando "you can sleep when you get home plan", I would recommend getting park hoppers and probably schedule something like this:
Day 1: Magic Kingdom all day. Reserve Fastpass for Thunder Mtn, Splash Mtn and Seven Dwarfs Mine Train. Maybe eat at the Castle, or Be Our Guest. Crystal Palace is fun, and depending on park times, you can have breakfast at 8am before park opens at 9am. Stay for fireworks.
Day 2: Seaworld. Get there early and ride Kraken and Manta when park opens. Plan the rest of your day around the sea lion/dolphin/shamu shows. Leave mid/late afternoon, hit the pool. For dinner, pick a fun dinner at a Disney resort, plenty to choose from: Ohana, Hoop-dee-doo, Whispering Canyon Cafe, 1900 Park Fare, Boma, etc.
Day 3: Hollywood Studios in the morning. Get there when park opens, ride Toy Story, Star Wars, Muppets, maybe Tower of Terror and Rock n Roller Coaster if the 9yo is up for it. Midday hop over to Epcot. Reserve FP beforehand for Soarin & Spaceship Earth. Wander the countries, plenty of choices for dinner, I'd recommend Via Napoli in Italy. Stay for Illuminations fireworks.
Day 4: Animal Kingdom in the morning. Reserve FP for Everest, Safari, Kali River Rapids. Walk the trails to look at the animals. Grab lunch at Pizzafari or Flame Tree BBQ. When ready, hop back over to Magic Kingdom until park close.
