Tara,
Easy answer. Hands down the best character dining experience for two boys that are looking forward to seeing their old buddy Mickey is
Chef Mickey's in the Contemporary Resort.
First, they breeze in on a monorail, literally driving right into a building. How cool is that!
Then Mickey and his pals (Minnie, Donald, Goofy, Pluto, Chip, and Dale) visit them while they dine on a breakfast or dinner selection that is far better than what you usually get at a buffet. Finally, when they are done they are just a quick walk (or monorail ride) from the Magic Kingdom.
For another option that is a bit off the standard dining experience, there is
Mickey's Backyard BBQ. It combines a great outdoor dining setting, live music, and character fun. And Mickey is the host, so you know he is going to show! It is only open on Thursday and Saturday evenings.
A good alternative, thought not always guaranteed to have that Mickey touch, is
Donald's Safari Breakfast in the Animal Kingdom. Great exotic setting, fantastic buffet food (who thought you would ever hear that?), and great character interaction!
I hope this has helped!
Have a magical (and delicious) vacation!