Several years ago, one of my closest friends was murdered leaving his two children orphaned since they lost their mother a few years earlier to cancer. I put out a call for book donations. I didn't specifically ask for "healing" books .. mostly light hearted, funny books. The children and the aunt who has raised them was appreciative.
I think almost a variety .. I'm not sure that there is a "healing" book that would work .. it may not be the right time yet. There is a group that has camps for children who are victims of violence ... I want to say it's part of Compassionate Friends .. but I know that is for people who have lost a child. I know my friends' children went to some sort of camp.
Also, some years ago a family of girls lost their grandmother who was raising them. They were being shuffled off to live with relatives ... and our church presented them with devotional books and journals. If something like this would be suitable for these children, that may be an idea.
I can't remember the specific titles sent to my friends' children. I do remember Lisa Yee sent some.
Also, a few years ago several kind blueboarders helped when I put out a call for books for a writer friend who lost her firefighter husband in the line of duty. These children were very young at the time.
So ... I'm not sure if it's necessary for it to be a book that speaks to the situation. Just some good light hearted, escape books might be a good idea.
Just my two cents. Sometimes you want an escape. Years ago when I had a miscarriage, I didn't want to read books on grief or the loss of a child or anything like that. I asked my friends for gothic romance! I hate romance. I wanted total escape.
So I don't know .. these are just my opinions based on personal experience.
I am sorry to hear of this situation. Thoughts and prayers go out to the families involved.