God gave marriage to us, and His original plan was for a husband and wife to be committed to each other as long as they lived. In other words, divorce wasn't part of God's original plan; in fact, God even says, "'I hate divorce,'.... So guard yourself in your spirit, and do not break faith" (Malachi 2:16).
Why did God say this about divorce? The reason is because He loves us and wants what's best for us, and He knows the hurt and anger and conflict that almost always follow in the wake of a divorce. Sadly, you're experiencing something of this, and my heart goes out to you. I want to assure you also that God knows what you're going through, and no matter what caused your divorce, God cares for you and your ex-wife and your children, and He wants to help you.
What can you do? First, pray for wisdom, and for a forgiving spirit. From what you say elsewhere in your letter, God hasn't been an important part of your life -- but He can be in the future, and He wants to be. Confess your sins to Him, and ask Jesus Christ to come into your life and change you -- and He will.
Then do whatever you can to communicate your concern to your ex-wife. Don't, however, react in anger. The Bible's words are true: "A gentle answer turns away wrath, but a harsh word stirs up anger" (Proverbs 15:1).