Hi I have the perfect soulution to your trip.
Day 1(non travel]
Today i suggest you go to Magic Kingdom and start off in fantasy land your dd3 will love all the rides!!!! if you promise the boys Buzz after this theyll be happy.Winnie the Pooh is a gentle ride with no scare factor you are simply travling in a honey pot through the story book. This attraction has long lines so i'd suggest going early, during meal times or during a parade, or Fastpass it. This is the same deal with all the rides in Fantasy land .
The next ride is Snow Whites scary adventures this is the same concept as Pooh but you see a lot of the witch and thier are some gotcha moments.
Dumbo is a ride where you sit in elephants outside and they go around and you can make them go up and down. Mickys PhillharMagic is fine for ds6 and ds7 but might be too loud and dark for dd3. This is a 3-d show where Donald duck takes over mickeys orchestra and it is loads of fun!!!! The teacups as you probably know are teacups where you control the speedv of the spinning so it should be fine for everyone. In Tommorow land the only attractions i would reccomend would be Buzz lightyear. You shoot and battle evil zurg! this is a great ride just like stepping into a video game!!!!! the tommorowland transit auhority is a great place to rest. If you need a break, it is also great to ride the train around the park. Mickey's Toontown is a fun place to go to get autographs and pictures with Minnie, Mickey, and assorted other characters. Again, go early, or at parade time to avoid long lines. Your boys will love the Indy Speedway, although it also can have some long lines. In Adventureland, Fastpass the Jungle Cruise and ride the Aladdin ride (like Dumbo only with flying carpets, and check out pirates of the Caribbean. This may be too frightening for some young children.
Our family always found it best to go to the park early, leave about noon and have lunch at the hotel, followed by a brief nap or pool time, and then back to the parks about 3:00. The parade crowds start leaving around then and it makes the park much easier to navigate. Hope this info helps you some what.