It's not a true breakfast buffet in the sense that you get up and serve yourself. The menu is far more limited, actually. But they will continue serving you food until you are ready to leave, so it's unlimited food, without leaving your table. I went once for Lilo and Stitch and haven't been back. It's usually Lilo, Stitch, Mickey and Pluto, though they may switch it up. When I first started going, it was Mickey, Minnie, Chip, Dale, and a few others, I think.
When in doubt, Google is your friend. Here's a price list and some information I was able to find by doing a quick Google search:
Lilo and Stitch Best Friends Character Breakfast - 'Ohanas - Polynesian