Agree with PP about Cosmic Rays. Along with the rib/chicken combo, they have a philly cheesesteak sandwich. That thing is HUGE, definitely could split that.
At Epcot, Sunshine Seasons has a couple sandwiches that are very good and large enough for kids to share. Also the asian station if they like chinese food.
At DHS Starring Rolls is another "sandwich" place. Totally different from Sunshine Seasons, their sandwiches are big enough for 2 adult (big eaters) to split. And for dessert you can get the huge cupcake to split if you wish.
For AK we always eat at Restaurantosaurus and get the double cheeseburger. It is good size, not sure if it is big enough to split. But depending on your kids it could be.
Enjoy your trip!!