Thanks for your kind words Jennifer! Every person in your party aged three and up on the Disney Dining Plan will get one table service, one counter service and one snack credit per night. As you are staying four nights, you will each get four snacks, four counter and four table service meals. These can be used at any time and in no particular order up until midnight of your check out day.
Given the ages of your children, I definitely think a few days at the Magic Kingdom are in order, but I do think four days might be a bit much. A day at the Animal Kingdom is a great idea, and I recommend spending one of your park days at
Disney's Hollywood Studios. The "Honey I Shrunk the Kids" play area is a great place for the kids to run and play, and other attractions such as Toy Story Mania, Playhouse Disney and the Voyage of the Little Mermaid make for fun for the whole family.
Wishing you a magical vacation!