Woody and Buzz are across from TSMM. Green army men sometimes walk around that area, too.
Mike and Sully meet (used to meet?) near the entrance to the Backlot tour, but don't know where they are now.
The animation building has sorcerer Mickey and others (used to be Ralph and Vanelope, changing to Big Hero 6). I've seen Incredibles there before, too.
Phineas and Ferb also have a meet and greet (kind of near the Muppets movie).
I have a 6 year old, but he's never actually used his own autograph book, so I'm 30+ (very plus) and I use one, lol!!