Nothing, although I didn't have to. They are little sponges, NOTHING gets past them. However careful you are, they sense stuff, hear stuff.
Unfortunately they were exposed to a lot of awful stuff, and now that I have come through the other side, albeit very scarred, I am told, and I am beginning to believe, that it was the quality of my mothering that has kept them as safe and wonderful as they are.
They are both happy, have loads of friends and are achieving beyond expectation (see where labelling gets you! Nowhere!)at school.
One of the things that I was told over and over again by my family, was that I was "a terrible" mother....this in front of my kids.
The longer I am truly No Contact, post therapy, the more I can see just how toxic and damaging it all was.
Ds watched American wifeswap.....not my choice, but there you go! He came to me and explained that they were so dysfunctional because they endlessly defined and labelled one another in a stream of negative ways, and he could see how unhappy this was making the children. He has learned so much too.
DD was involved in some of my inner child therapy, unbeknownst to her of course! She helped colour in my pictures. She knew the characters and the story without any prompting whatsoever from me. My therapist assured me that this was ok.
Sorry, I've gone on a bit, but the simple answer is that you don't have to tell them anything, they already know, and that's why No Contact is so crucial for their future mental health and relationships too.