I would be tempted to give her a few days to think her decision through but then ask her about it.
I think if you leave it to your W tell the kids, you are throwing her under the bus at this point. You should be there for your kids, if nothing else. They will ask a lot of hard questions your W will have to answer. I agree, she does need to own this. They will know you are not on board. You may want to have a conversation with her how you are going to tell the kids prior to telling them.
What would the plan be for the kids if she moved in with her mother? Would all of the repsonsiblity fall on you or does she have some kind of shared arrangement in mind?
