Dear Grammy57 - I am sincerely sorry for you, your daughter and your remaining grandchildren in this appalling tragedy and bereavement.
If your daughter wants to stop drinking, then some of the various associations such as AA or Blue Cross can help. Unfortunately, no-one can possibly stop drinking too much unless deep down they want to, and this may just not be possible for her in her appallling distress right now.
Bereavement counselling or groups might well help you and your grandchildren, and might help you daughter, but again it sounds to me as if no one can reach her right now.
I mean, if you, her mother cannot, who can?
I agree with the sentiment that if you honestly fear your daughter is at risk of committing suicide herself, you do need to get her GP to take that risk seriously.
You all need help - are the children's school or schools on board? Surely, there is grief concelling for children?
It sounds as if you are the only relation your daughter and her children have. Have you had a word with your doctor about your situation?
I know you are probably thinking, oh I shall cope, because I have to, that is what mothers do AS LONG AS THEY CAN, but no-one can go on coping alone indefinately, so please do find someone you can lean on.
Your daughter is understandably so devastated that she cannot cope, so as far as I can see you are the only adult trying and to a great extent managing to cope.
It must have taken courage for you to even write your post here, and I hope you will stay in touch with us . I have been greatly helped by the kindness of people on the bereavement thread myself, and I hope you will find it helpful too.