It sounds like you have a wonderful upcoming trip to Walt Disney World that will be filled with many unforgettable moments with your grandchildren! Since they are younger, I think they might enjoy breakfast at
The Crystal Palace at the Magic Kingdom. It is located right on Main Street in the park, so it is easy to make it your first stop before heading out to the attractions of the park. You'll meet Winnie the Pooh and other friends from the Hundred-Acre Wood. When we eat here, I try to get our reservation
before the park opens (avoid Extra Magic Hour mornings) because you'll be able to enter the park early and likely get some amazing pictures on Main Street with few guests around.
Another great spot for character dining is
Chef Mickey's at Disney's Contemporary Resort. This resort is right next to the Magic Kingdom so you can walk to the park or hop on the monorail when finished dining. The breakfast has Mickey and his friends and is a lot of fun for guests.
If your grandchildren have a love for Disney princesses,
Cinderella's Royal Table epitomizes the Disney princess experience as guests dine in Cinderella's Castle. This also offers table service instead of a buffet. Please know that this meal is incredibly popular so you'll want to make reservations as soon as you can. If you are a Disney resort guest, you can make 10 days worth of reservations when you are 180 days out from your arrival date. If you aren't a Disney resort guest, you can make dining reservations 180 days out from the day you'd like to dine.
If we can help with any further questions, please let us know. Wishing you a magical trip! -Kara