I don't see what the problem is with kids in either J or F. My six year old daughter regularly flies in J and knows how to behave herself. In fact is off to SFO in J with her mother today.
We all went to IAH last Easter and the young lady had 1F on a 777 and was complimented on her good behaviour from the crew. It's not the kids, it the control of them - the same whether you are on an aircraft or anywhere else.