"Divorce Care" is a program offered around the country. they also offer a year round email daily encouragement "one day at a time" that will be helpful whether or not you can ever find a group.
I attended one and know many who have attended a program in their local areas and everyone who participated indicated it was worth the time and effort.
As others have said, it does get better. You have a LOT of life ahead of you. Your kids will take their cue and need to see one sane parent.
As horrible as this all is, you have your kids and it sounds like they are healthy. There are many two parent families with ill (or deceased) children who would trade spots with you in a heart beat.
My X remarried quickly and she has the kids. I have nothing except for my integrity and a wonderful relationship with the Lord (and my children- who are healthy). I am indeed a blessed man.
It will get better.
(p.s. stay clear of yours sister, to treat you as she has, she has bigger problems than you do).
Committed2Him- "C2H" All Things (Back from Spain!)...18