HA! They're very well behaved (really!) and we travel with them a lot...our last flight (4 hours) the row in front didn't even realise we had the kids with us until after we landed!
I'm just conscious that CX First is really quite a dinky lounge where it's hard to find a quiet corner - by the look of things QF has a kid zone and more little spaces for us to go and hide out with a strong drink...