One reason I wanted to reprint your letter is because I hope it will be a warning to anyone who might be tempted to go down the same road you've taken.
The decisions we make in life always have consequences -- always. And bad decisions (such as the one you took 30 years ago) always have bad consequences. Elsewhere in your letter, you admit that over the past 30 years you've drifted from relationship to relationship, never finding lasting happiness -- and only bringing unhappiness to others. Sadly, your children's refusal to have anything to do with you is only the most recent consequence of your way of life. The Bible's warning is true: "Do not be deceived: God cannot be mocked. A man reaps what he sows" (Galatians 6:7).
What is your real problem? Your real problem is that you've left God out of your life. You have lived only for yourself, thinking your way is better than God's way. But it isn't, and now you're paying the price in loneliness and rejection and unhappiness.
But it doesn't need to be that way. God loves you, and the most important thing you can do is turn to Christ in repentance and faith, and turn your life over to Him. Why delay any longer? I can't guarantee your children will change their attitude, but God will change you, and with Him there is always hope.