As nice as the idea of having the perfect child sounds I think it's too comparable to Adolf Hitler's view of the master race. He encouraged all kinds of things to make sure that the ideal German met certain guidelines and even exterminated those who weren't; would our genetically altered sons and daughters want to expand upon his ideas and their own creation? It's possible that if they believe they're perfect, why wouldn't they use this technology to essentially create the perfect race?
Not that all genetically modified children would grow up to become neo-Nazis, that was just a very extreme example and highly unlikely. But it is a fact that many would just have children and use the technology for fashion purposes like "designer infants", born to do nothing more than be pretty, afterwards they grow up and have no other purpose in life as far as their parents are concerned.
On a positive note though, we could potentially eliminate mental and physical disfigurement or disorders and everyone can begin life healthily. Who wouldn't want a son or daughter to begin life strong, naturally intelligent and be a charmer?
I think we should let nature control how we're born and how we leave this Earth, because humans would no doubt abuse this system as we naturally do. Sure this technology may be created by responsible people, but who will it be handed down to, and how long will it be before the inevitable abuse of such control over human life?