We believe pretty strongly that positive behavior is a reward unto itself. I would hate for DD to get the idea that she should only be polite/kind/helpful if she is going to get something out of it. This system you are discussing gives me the creeps, to be honest. When your kid is out in the real world and nobody rewards him for these things, where will the motivation come from??? These are not behaviors that a child should engage in simply because (and when) he wants an ice cream cone.
DD3 already likes it best when all of her family is happy and she does her part to contribute to family happiness (most of the time). She uses please and thank you and even "may I?" just because that is how we talk to her.
