My W and I had a dinner with the kids to let them know that we were separated. However, I had already had a talk beforehand with the kids and it was very tough because my son broke down.

I dont think it wise for you and your witch to have the discussion together. I can see there being too much animosity for it to be beneficial for the kids. You are much better in speaking to your children about a delicate situtions without having the ears of a batchitt crazy angry slut listening in.