From a lot of the threads I've seen, Mickey's BBQ seems to be geared towards younger kids unless your son likes to dance and parade with the characters. My fifth grade son would probably disown me

- lol.
If you want to meet Mickey and Pluto (and Chip and Dale) and are going to Epcot, Garden Grill is a good breakfast with characters spending time at your table - so easy to get a picture without the insanity of one of the buffets (have also heard a lot of people say they like lunch/dinner). A non-park option is O'hana for breakfast - I've heard breakfast is good and Mickey is usually there with Lilo and Stitch.
Whenever I tried to twist my older son's arm about characters, he said if he had to pick, he would pick the Beast, Donald, Stitch and/or Goofy. So, I would also consider BOG for dinner where the Beast is... I think Tusker has Donald (we've never been - we don't go to Animal Kingdom as much, but heard good things)
I have younger kids including a daughter, too - so we also do Chef Mickey's for breakfast (don't care much for food at the other meals) because you get to meet all 5 of the big characters (mickey, minnie, donald, pluto and goofy) which makes for a good classic picture and Akershus for the princesses (if we can get a PPO reservation so we can rope drop the Frozen ride - usually both Cinderella and Belle are there).
My nephew's didn't like the princesses much, but they did like Cinderella's Royal Table because they got to go inside the castle.