Now that you mention a 12yo boy and wanting a character meal I'd say Chef Mickey's. Its loud, rowdy and has 5 characters: Mickey, Minnie, Goofy, Pluto and Donald. There was a teenage boy next to us with his grandfather and he seemed to love his time there.
I think Pooh is a bit babyish and many 12yo boys wouldn't want their friends to see them in photos with Pooh or his friends...lol.
Since Stitch is kind of a "bad" boy the character breakfast at 'Ohana might be fun for a boy that age.
For food I stand firm on my suggestion of Boma. It is hands down the best breakfast buffet at WDW. If your 12yo loves to eat, that is the buffet for him. There will be lots of familiar breakfast fare, made to order eggs, omlettes, pancakes, amazing french toast, chocolate chip muffins, fruit, yogurt, meats. My 9yo is picky and he loves Boma breakfast, calls it "awesome".