We've done GK for dinner twice, once in Sept 2012 and again this past July. We didn't see Baloo either time. Maybe he appears at the critter breakfast at storytellers? We have done all of the character meals except storytellers and have not seen Baloo.
You may want to go change your approach a bit. Saying "my girls are expecting Baloo and I don't want to disapoint" is setting you and your family up for trouble. If it was Pluto or Minnie, that would be easier, but I think the likelyhood of seeing Baloo is pretty slim. So, maybe tell your girls that there are lots of characters at the dinner and Baloo might be there or he might be in the jungle, but they'll have fun with whoever is there.