The character breakfast depends on the time of year you go - during busy times it's on Sat and Wed; non-busy times on Sat only. It is not a buffet breakfast, nor is it pre-plated (like Olivias); The characters are limited, though great: goofy and max (I love the Goofy movie, so I get a big kick out of goofy and max).
The buffet at Sonya's last time we went was very nice, but not cheap. I recall it was $18, maybe $20, but also included a glass of Champaign. The buffet had an excellent selection of items, and in my humble opinion (or not so humble) was well worth the expense. We would do the buffet again with no hesitation - though I think we'd do what we did last time; leave the kids at an organized activity and "sneak" away.