It touched me deeply to hear the details of your wife's fight and your sorrow. I can imagine your children's pain unfortunately after losing my mom to cancer. Losing your mom is about as tough add it gets.
Keep sharing your story in detail about your wife's fight with cancer. It will help sort everything out in your own heart and mind. I can tell by reading your story that the sorting has been underway for a while and you are way further along by this point than I was. When we go through tragedies, some things we thought that were important facts weren't and other stuff is more enduring. That process continues throughout our lives. You have an awesome family and a wonderful understanding of the plan of salvation.