I deleted the posts above from schoolmarm who placed all the blame on you. Her opinion was short-sighted and wrong.
We're here to support each other, not to judge.
I, too, cheated, 3 times! And while I admit I should have gotten a divorce beforehand, I now know I was desperately seeking love from someone because my alcoholic ex was putting me through hell.
Telling the children about an affair, especially young children, is far, FAR worse than the affair itself. If you spouse is threatening to tell, you need to tell them first, so they can see the situation from your point of view.
Since your husband is already using your children as pawns, they are already being mentally abused. You need to get out NOW. Please download my book (which started this forum) to see what you need to do to prepare. You can also read about my affairs there, and how my ex told my kids about them, too. It's free at:
My children no longer judge me for my infidelities. Through counseling and many long discussions, they understand why I did what I did. In fact, they don't blame me at all for what I did. One of my affairs (the last one) is still a friend of my new husband, Richard, and the children don't mind at all. He's just another "friend of the family."
It's not what you've done in the past that matter. It's what you do now to ensure your childrens' emotional and physical safety.