Big hugs to you hun. This is a very difficult thing to go through, but you seem to be doing a great job of coping so far.

It is very important that you are able to tell the girls in a way which will reduce their anxiety as much as possible, and also make it clear that this is in no way their fault. It is best done together, and you should both agree on what will, and won't be said. It is best to be honest, but without telling them anything they don't need to know - as in don't expect them to understand things beyond their years and don't blame each other etc. Give them lots of reassurance that they are all still loved and will still see plenty of both parents etc, and that you will try and keep things as much the same as possible.

Best of luck hun and please take care.