With respect to kids in First, if your children are well behaved by all means keep them up there with you.
However, if you have no control and use the excuse "well kids are kids, what do you expect?'. Please seat them back in coach, you will be doing a diservice to your fellow pax who pay for 1st to enjoy a quiter more relaxed environment.
I say this because I have seen both. I would like to give credit to parents who still raise children who know how and when to behave. If your children know ho w to comport themselves, then there is no reason why they should not be up in First with you.