Dear wanttobehealthy, my first thought as I read your post is the memory of one o f my biggest "take aways" from my child developmental courses is this: Children who are going through a crisis of some sort (divorce, housefire, major move....etc), do better and recover best when their sense of security is provided for in 24hr. increments by an adult who appears to be in stable control. Children look at their lives in terms of the "here and now" satisfaction of their needs for security. They respond to PREDICTABILITY and structure--and an environmental tone that says: "My caretaker seems stable and caring--so I am o.k." A schedule that is as normal as possible under the circumstances--and above all---predictable. Absence of chaos. In other words--"I know what is going to happen today---I am going to be safe; and be fed; and will not be deserted; and know that I can go to sleep tonight and trust that everything will be o.k. when I wake up." (You get the picture). Apparently this has been studied extensively in many kinds of disruptive circumstances, and this one principle seems to stand up. The children don't necessarily look at the situation in the same way that the adults around them do. They do look to the adults for signs that their immediate needs are going to predictably be provided for. At least one calm, stable and loving adult that can be counted on is essential to normal development. They need calm--even in the eye of the storm.
As far as what to tell them---I do know that the basic truth (as opposed to lies) IN AGE APPROPRIATE TERMS is another basic principle. Let them talk and express their feelings without judgement or pressure. I remember from my kids that their feelings and questions usually come out later(often at unexpected times) as they are processing things themselves. When my kids got back from a visit with their dad--they didn't want to talk much about it. Gradually, as the week went on--they would make comments on their own. I learned to NOT ask questions--I knew they would bring up issues or experiences in small increments, over time.
I am sharing these general thoughts with you in hopes that they might give you some guidence as to how to handle things. I know that this is a tough position for you. Nothing about this crap is easy.
We are here for you.
sincerely, dandylion