what about just talking to a social worker independently then to discuss healthiest ways for children to go though this type of tragedy? There is a lot to process, and sometimes when we are forced to deal with the emotions and stress of all this, it can be difficult to look at it as a whole.
This way you have better idea of what they are going through and what their needs will be at this time. I think it is great that you are not saying anything negative about their mother.