Gordie, for the younger kids I wonder if you could check into "The Fall of Freddie the Leaf". It is written I think to help kids with grief from death, but I think the themes will play out for this situation as well and as we know, the feeling of loss for a marriage or a family feels like a death. Maybe a chaser with the book "Parts" about how weird stuff that happens to our bodies is completely normal. It is funny and reassuring. I think the little ones just need to understand that change is ok and in fact a normal part of life.