I agree with V here U, wife has made it clear that she cannot see past her own needs, to see the needs of her children. Given that you know your D15 is a sensitive soul, someone preferably a safe adult who is stable needs to check out where she is at.
Your daughter may well need a debrief now, before you and W can negotiate a time to talk to the kids. I feel wife has given a clear indication that for now, she is going to prioritise, her crisis over that if the children. As you said U, you believe your wonderful children see you as their rock. I don't disagree, I do believe that your darling daughter might need her dad sooner rather than later. You got this U.
Ps. Beautifully managed with your S18. And again I agree with V, he has made his wishes known, they need to be respected. They may change, but for now, respect what he is telling you. The children need to have some control over what they can. Because certainly there will be so much they can't.