What I do with MY kids is slice as much as I want to give them. If I get any complaints, I say "Life isn't fair. If you don't like the cake, I'll eat it for you."
I think the magic of the "Cut n' Choose" method is it's simplicity. By the time we get a ref and tell our favourite features.. jeez, the ice cream would be melted.
"Life is hard. Get used to it. Suck it up!" Hahahaha! It's funny because it's true.