I am going to make a prediction--virtually all the replies from the experienced and the wise members of this board will tell you "DON'T DO IT!" They will tell you the potential risks are just too high and too predictably unfortunate. They are the voices of experience and reason, they will be right.
Maybe there is a contrary view? What if your "close friends" have as much to lose from disclosure of these activities as you do? "Close friends" don't always stay close and can become estranged, so don't ignore that potential--guard against blackmail by knowing that you are not the only ones at risk.
Affairs involving sex are risky, even with just two people, but life would be boring and not rewarding if everyone was unwilling to take the risk. Whatever you do, keep us posted.