How many serving do yu think it is realistic to expect from a 8,12 inch rounds?
Although many people say the servings are too small, I cut every single cake (client or family) per the wilton wedding chart, so a 2-layer 8" serves 24 and a 12" 2-layer round serves 56. No one complains and many people ask for a smaller piece.
Here's how I cut cakes to achieve those servings: http://cateritsimple.com/_wsn/page10.html
Here's the wilton wedding chart that I go by to determine pricing (and oh yeah you can use it to determine servings, too, if you want! ): http://www.wilton.com/wedding/wedding-cakes/wedding-cake-data.cfm