I have experience of taking 2 kids on BA (mines started at age 2 and the oldest in now age 8). Have done WT, ET and CE with them but not CW or F. The most important thing to my mind almost more than travel class is getting the right seats so you can sit close to your child and talk to them. I think that this is important for both their and your enjoyment and their behaviour.

In CW make sure you get one of the middle seats next to them. IME, they will love the opportunity for their parent's undivided attention and respond brilliantly to it.

Don't worry about people thinking that kids are not supposed to be in a particular cabin. My last trip with them was CE from BGO. Bloke opposite clearly did not approve of children in Business and keep given disapproving looks and muttering. The children were impeccably behaved despite it being well past their bedtime and my wife and I were complemented on that by other passengers and the crew when getting off the plane. I think that annoyed the grumpy bloke even more. He had got himself wound up to be righteous and annoyed and we had denied him that opportunity.