I do not know your full sutuation so please bear with me.
Your first explanation W has OM in her life now and so it does not make sense for her to hang with us would suffice with some tweaks. The I need to say that it's clear that W is not interested in restoring our family so we will need to stop acting like one is the expresion of bitterness and sarcasm that children can do without.
I think you should never make it about "we" but "me". Saying that mom has found someone else so it makes no sense to continue with memakes it more about the 2 of you and not that she has an issue with them. Even if she did.
I have known women whose husbands left them and neglected their children for a while or permanently. Fantastic women but there were those who used the kids as a weapon or bargaining tool and those that defended "daddy" whatever was happening with their R.
IMHO Even if a parent neglects a kid, there is no need for the LBS to hammer it in with "daddy doesnt love us" expressions. The LBC (Left Behind Child) who will have his heart broken by his parent at some stage if that is how it is going should feel and see it for themselves. Your job should be one of solace, comfort and protection. Not validation.
Children at certain ages with break ups have insecurity, pain, confusion, anger .
The examples I have found to work are those where the child was told the situation with sincerity, without the harsh reality. That will unfortunately come later as the new life unfolds.
