That is a great idea! One time, my wife and I got a room at a local casino and invited a guy to join us. We checked in and had a couple drinks while waiting for him to arrive. After he arrived, there was some small talk. I then politely excused myself while they got to know each other. I went down to the casino to gamble while he got my wife naked and they played. After the longest 45 minutes of my life, my sexy wife texted and said they were ready for me to come back. As I neared the room, I could hear my wife moaning and clearly enjoying herself. As I entered the room, I saw my wife riding her new friend for all she was worth. I stripped down as fast as possible and my wife started sucking my dick while her new friend continued fucking her. We took turns fucking her until he finally blew his load up into her mouth with her swallowing every drop. He then left and we got to keep playing until I was exhausted!
This gave her all the alone time she wanted but included me as well. I would have been fine with her finishing him off before I came back, but also enjoyed watching him fuck my wife and joining in. It was hard focusing on gambling knowing my wife was getting plowed up in the room. It did give me something to pass the time. And I won a few dollars as well!