nujax,
I'm very tempted to suggest that the three of you meet before anything takes place. You may get a different point of view from someone else but my reasoning is that Mr. should be made very well aware that you're okay with any activities that take place
and that you're going to hear about them.
This is as much about your wife's safety and well-being as it is about keeping the air "clear". Any ground rules that the two of you establish should be well-defined to this gentleman, as well, with no questions asked.
If I can say this without seeming callous, you aren't sharing your wife with this man for
his benefit. It's about your wife and you. Not trying to throw an ice pack in your lap, if you get my meaning, but there's nothing in this worth taking any unnecessary risks.
Frankly, I wish you both the best of luck with your adventure especially since Mrs. Van and I have an ongoing fantasy very much like yours.
Van