Hi Sheila:
You are a wonderful grandparent. Your grandchildren are going to love spending the day at Magic Kingdom. It's a Park where you "can't-go-wrong." I have a five-year-old and a three-year-old and have been traveling to Walt Disney World with them since they were infants.
While only a portion of the many Magic Kingdom attractions, our family always enjoys Buzz Lightyear's Space Ranger Spin, it's a small world, Jungle Cruise, Mickey's PhilharMagic, Peter Pan's Flight, The Many Adventures of Winnie the Pooh, Pirates of the Caribbean, Tomorrowland Transit Authority People Mover, Haunted Mansion, and
Monster's, Inc. Laugh Floor. They can also hop on a train to take a ride around the park on the
Walt Disney World Railroad. Your grandchildren, if tall enough and brave enough, may also be interested to check out Splash Mountain, Tomorrowland Speedway, and Big Thunder Mountain Railroad.
Enjoy your trip.