Hambeak
I am glad that you posted here, and hope that the advice of others has shown you that you are important to us and that we hope you are feeling better soon.
I am wondering if perhaps your children are angry with you because they blame you for the breakup of the family. They may have said things to you to try and hurt you because you have hurt them. The words they used sound like this to me.
If you do contact them, yes, make the words short and meaningful. Perhaps you could tell them how proud you are of something they accomplished in life, even back in elementary school. Tell them they mean everything to you. Perhaps they will not respond immediately; however, they will not be able to say that dad ignored them. Perhaps they will soften in time and want to see you or correspond with you.In fact, you could even send each child some stationery and stamps to write back to you, or send your e-mail address. That way, if one wanted to contact you without their sibling's knowledge, he or she could.
I still feel that even though humans (the Borg) may cast us off, God never adandons us. Jesus died for each one of us on this earth. This thought still brings me comfort. Try to do things for others. This has a way of boosting your spirits and we can just but look around us and see that so many need us.