Willowman
My experience of taking my infants in business class is that they were charged at 10% of the full adult fare. That's for no seat, or guaranteed basinette. I've also paid the discounted adult fare for when they were children, as often this has been cheaper than the child fare at 66% of the full adult fare.
FWIW, my own view is that I expect my children to behave on an aeroplane, in any class, in the same way they should in a resturant or hotel. Words or worse will be had if they disobey.
cur