I agree that discretion and sensitivity is very important! But there are subject matters that children and parents need to discuss that very well might be upsetting but necessary. So where do you draw the line? I am actually just curious!
It will hardly be comfortable the day CTH's daughter comes to him and says "dad, I just got my period" or "dad, I have questions about sex" but he is going to have to deal with it, right? My thought pattern would be if his kids know HE feels some subjects are off limits they will follow suit and be very selective about what they keep sharing with him.
My own father was very selective in what he would discuss with my sister and I about ANYTHING. Instead of trying to guess what was suitable conversation so he wouldn't get all bent we decided the best course of action was to tell him nothing. He got pleasantries from us and that was it. Kids catch on quick.
It's a dilemma I am sure. The divorce is between two adults that happen to have two children. Since custody is shared there will always be some cross over discussion I would think.