I've made mini-muffins before and it doesn't take much to fill'em. One box of cake mix (or 5 Cups batter) would probably make at least 50-60 mini-muffins. When I made them, it seemed like it made closer to 70 but I never counted.
Birthdays are just nature's way of telling us to eat more cake.
I dunno. I have the mini muffin pan of Pampered chef and when I did bite size cupcakes for my kids I didnt get two pans out of the mix.... almost but not...it has 24 spaces on the pan. Then again, it was a white cake mix.. I think perhaps it would be just enough if it were another flavor.