Hi Michelle,
My children, ages 5 and 10, love all four of the theme parks. However, in my opinion the best two theme parks for guests their ages are the Magic Kingdom and Disney's Hollywood Studios. Based on my experience, I suggest concentrating on those two first and then visiting Epcot and Disney's Animal Kingdom.
My family also loves the two water parks at Walt Disney World. My children prefer Typhoon Lagoon over Blizzard Beach but both are absolutely fabulous! The theming is fantastic. We have made trips to Walt Disney World for the sole purpose of visiting both water parks.
My children love Disney Character Dining. On every trip, they want to have a meal at Chef Mickey's in Disney's Contemporary Resort. We also love eating in 'Ohana in the Polynesian Resort and at the Whispering Canyon Cafe in the Wilderness Lodge. An Advanced Dining Reservation can be made up to 180 days in advance. Be sure to make some reservations as Walt Disney World has some fantastic places to eat that are very popular; some of the restaurants book up very quickly! Reservations can be made
here.
I recommend getting a tour book to Walt Disney World. My two favorite are "The Unofficial Guide to Walt Disney World" and "The Complete Walt Disney World". They take different approaches to planning a Walt Disney World vacation. I suggest looking at both in a book store and seeing which style you prefer!
Enjoy planning your vacation and write back if you have any more questions!