Just thinking about the 4 yr old and I wonder if it is worth giving her some pencils and some paper...Not pressuring her into drawing anything about what happened, but just getting her to draw. Chances are if she witnessed something it will be at the forefront of her mind and she will draw about it..That will open up an avenue for a few sensitive, appropriate questions. It is more for her than anything as at 4 yrs old, kids have a difficult time expressing how they are feeling. I am suggesting this, as the same thing was suggested to us after a traumatic situation in our family that my 4 yr old unfortunately had to deal with.