It's a risk that's what makes it exciting, when my wife would go on deployment or out to the field training I knew she would probably fuck another soldier, my wife never used birth control so I knew there was always a chance she would get pregnant, a few times she came back pregnant but the pregnancies ended in miscarriages, there was one time I got her pregnant and she had the baby, 6 months later she got pregnant again and had our second baby but this time she was only 90% sure it was mine because she had fucked another soldier a week before I fucked her after coming home from deployment,
Enjoy your experience with the 3some it'll be an amazing experience to watch the expressions on your wife's face as the guy empties his balls in her womb, watching another man making your wife cum will be the biggest trill.