Suzanne your children are going to have an awesome time on their first trip to Walt Disney World. Few events are happier than seeing a child enjoy the Magic Kingdom for the first time.
Planning my family's itinerary on our Walt Disney World trips I consider a few things:
Extra Magic Hours, dining reservations, and which attractions we most want to experience. On our last trip we visited Disney's Animal Kingdom first because our youngest child decided she was ready to ride Expedition Everest. On our second day we headed to Magic Kingdom to take advantage of an early opening, and ended the day at Epcot to eat at Le Cellier Steakhouse.
Following a similar model you might plan to visit the Magic Kingdom on April 19th when morning Extra Magic Hours are offered and on the day you eat at Chef Mickey's since it is located so close to the park. Consider taking advantage of Extra Magic Hours at Epcot on April 20 and Disney's Hollywood Studios on April 21. Water parks tend to be more crowded on weekends so perhaps plan a weekday visit. Are your children excited about Space Mountain? Then head to the Magic Kingdom as soon as possible.
Do make dining reservations as soon as possible. Arrive at the theme parks at opening to take advantage of the lighter early morning crowds. The Moms Panel wants your children's first visit to Walt Disney World to be as special as possible so please contact me if you have additional questions.