We've been to Mickey's Backyard BBQ the last two years (07 & 06) and our kids loved it (at ages 3.5 & 1.5 and 4.5 and 2.5 respectively).
The characters are:
Mickey, Minnie, Goofy, Chip & Dale
Mickey, Minnie and Goofy are in their "western" outfits including cowboy hats and Chip & Dale are in Chef's outfits with Chef's hats.
Lots of dancing for the kids including a train around the pavilion with Goofy leading. Food is pretty good and beer and wine are available (and free).