Also, check with your local grocery stores. Our's can donate up to $25 per event and that was about 4 cakes per store!! We chose not to open it up to any parents because we didn't know what we would be getting! Our teachers stepped in and baked remaining items needed since we didn't need to much more after donations from stores.
Hope this helps and good luck!!
We do a bake shop every year with our spring carnival and do very well. Whole pies and breads are top sellers because they take so much time to make yourself. We sell whole pies for $6-$7 depending on what they are(cream pies and more expensive or unusual fillings sell for more). We ask folks who are baking cookies and brownies to wrap them individually or in groups of 3 so we can price them so kids can purchase. Ask people to make less common things--instead of chocolate chip cookies, I made giant chocolate chunk/walnut cookies. We also sell pie and cake by the slice, but that's because we have a restaurant type operation for the carnival, but this could work for a bake sale too. For this I made a devil's food cake with a cooked frosting called seafoam(Better Homes and Gardens cookbook under seven minute frosting)then drizzle melted chocolate down the sides and a french vanilla cake with the seven minute frosting and strawberry slices in teh middle and whole strawberries on the top. We have just regular cakes for sale but they don't go like the more elaborate. We even had a mom who had taken a cake decorating class make a Scooby-doo cake that we sold for $12. Good Luck!!!