Island Man - completely agree. My Catholic schoolteachers fully accepted that omnipotence did not mean that God was totally unbounded, it was more that God could do anything he chose to do. I recall one example they used was that God could not make something that was both entirely white and entirely black, but he would have no reason or desire to do so, having himself created the laws of the universe which made such a thing impossible.
I'm an atheist too but I don't think arguments of this nature are going to dissuade believers.