I think that is a great idea. Sometimes breaking up the day is a fantastic way to recharge and refresh during a busy day at the parks.
Not too many of the character meals are offered at lunch, but there are ones that are I think would be perfect for your kids. One of my kids' favorites is Tusker House in Animal Kingdom. It is a great place to catch Donald in his cute safari gear! The lunch is a hearty one with lots of options that are not your typical buffet fare (ie, spit-roasted chicken, roast pork loin, and the warm banana cinnamon bread pudding with vanilla sauce). Characters are also available at breakfast at this location, but not at dinner.
Another fun one for the younger kids is Hollywood & Vine in Hollywood Studios. The characters from various Disney Junior shows make appearances to greet the tables and sign autograph books. The food here is super kid-friendly and the giggles are a plenty. I have heard that a new addition to this character meal is Jake from Jake and the Neverland Pirates, but as with all character meals, characters are subject to change and without notice.
Some other favorites of mine that are not necessarily character meals are Sci-Fi Dine-In Theater, Coral Reef, and Beaches and Cream. At the Sci-Fi Dine-In Theater, you eat in a car while watching a "drive-in" movie. The panoramic view of the Coral Reef is a great way to play "I Spy" with the kids looking for different sea-life while waiting for your meal.
Beaches and Cream is a fun little old-fashioned soda shop that offers burgers, fries, shakes and sundaes. It is at the Yacht and Beach Club Resort and does not take reservations, but a fun place to go, nonetheless! If you are feeling daring, try the Kitchen Sink!
Bon Appétit
~Allison L