I have a two year old and we fly him back and forth to the US twice a year to visit family. We fly in First/Business as it is part of my ExPat package. My son is generally very very good on the plane and we are often complimented on his behavior. Part of the problem is delays. As a parent knowing when I am going to have my son on the plane I time his sleep patterns for several days before hand in order to have him exhausted when we take off. On 1 Jan we were returning to CDG from PHL on USAirways in FC. The plane was delayed three hours and in that time despite heroic efforts on my part my son fell asleep. When we took off finally he woke up in a horrible mood and screamed for the first hour of the flight. I tried every trick in the book ( I did not then and will not ever resort to putting my hand over his mouth...that would only serve to get most children I know even more freaked out!) but not much could be done. This being said my son was on a full fare FC ticket (almost $7,000) and my wife, son and I were the only passengers in the FC cabin.
Another point is that in FC/Business class on Transatlantic flights you will have your in seat video which gives you a good chance to have your child amused while you head home.
I would rather have a plane load of children all screaming than take another trip with some of my past Business class mates....when was the last time a child defecated on the drink cart/stormed the cockpit?