Mac -- thanks for the guidance. Let me provide a few more details. She contacted him at my request. This is an idea we've been exploring for years. The fantasy started with strangers, then moved on to people she knew, particularly men she dated (the trust made it more realistic for her, which of course turned me on).
She looked up a couple different guys on facebook, and this guy was still single. And as I said, their relationship was never serious. So he was the natural choice.
Our latest version of this fantasy would be a 3-way, but mostly him and her playing while I watched.