I think with the piece of paper - the D. It's easier to have a real talk with her about how you won't be doing things as a family because you aren't a family. Your family is now you and your S.
You say that she doesn't get the message. Maybe you aren't communicating the message as much as you think.
Personally, I'd stop with "I have plans," I'd just say "we talked about this." I think you need to stop saying that the only reason you aren't doing things as a family is because other things get in the way.
The D also gives the freedom to have a frank talk with the XW. I think people come here and they get the avoid R talks message beaten into their brains and they see every talk that's not small talk as an R talk.
