i'd get them to get a hotel room...not sure about going to someone's place to bang their wife....you might end up being the next "precious" from Silence of the Lambs in a hole.
there was a guy that went to a racy nightclub I had been to who was picked up by this really pretty girl and she took him back to her seedy motel room.
Long story short, she tied him up and then some guy dressed up in a spiderman costume came out of the bathroom and buttraped him.
That dude is probably gonna sit there and jerk off while your banging his wife. He'll probably end up giving you a money shot when you least expect it.
Personally I don't feel too comfy letting someone watch me having sex (live) and jerking off all in the same room.