Well, you are Catholic as well. What is
your opinion of your wife having extramarital sex with other men? My suspicion is that you, as well, are wrestling with this question ... you, too, know as devoted Catholics that it is wrong BUT you need to justify it in your mind and her mind as well. And you're asking others, here, to help you with this.
Personally, if my conscious tells me it's wrong, then it's wrong. That's where your wife is now .... aware of what the Catholic beliefs consider right from wrong.
We can't justify your wife's participation in this type of sexual activity, but we can provide our opinions. If it makes any difference, my wife & I wrestled with this topic once we married and particularly when we started planning our family. We're devoted Protestants with heavy religious background from both sides of our families. We managed to justify it by establishing parameters to the activities and agreeing to not participate in sex without the other's acknowledgement. Its worked good thus far as we've been married 22 years now.
I've attached a research link to a lot of sources to reference and consider as you construct your own reasons & justifications to what your wife now wants. Just remember this is a couple decision and if one has trouble with doing it, the other needs to either respect it or justify it to his/her mutual satisfaction.
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By the way, these articles are simply to establish a groundwork to start your research. Best of luck!