We love to have breakfast at Minnie's, and though we always love to sit outside, we've never had any problem meeting numerous characters. Our last breakfast there, we were the only ones outside for quite a while, and the characters made it a priority to come out and meet us. Chip even came played peek-a-boo with my daughter several different times, and they were busy inside.
It sounds like it was definately an off day when you went, but I wouldn't hesitate to try outside seating again. The view is lovely, and the pictures are gorgeous. If you have the same trouble again, I would nicely let one of the hostesses know that you're having trouble meeting characters.
Hopefully, next time will be great fun for your family!