I am so very sorry, I have no doubt that your husband loved you and the children with his whole heart.
Sometimes we can back ourselves in a corner and can not see a solution or a way out in our delusioned drug soaked brains & we will come up with a answer to stop the pain.
Unfortunately we don't really realise it is forever and the pain that we will leave behind.
In our delusions, we can think we are doing the right, the only thing.
Are you and the kids seeing a grief counselor or therapist?. I think they can help, just talking openly and being reassured that all your feelings and thoughts are normal in all this madness and great loss.