Toi:
And I have a personal relationship with many fine couples who have shared a Shabbas/Yom Tov table with my wife and I. You know what happened at those meals?
We had double the laughter, double the food, double the divrei Torah and double the zemiros. It’s called hachnosas orchim, and it’s been the Jewish practice since the very first Jew. If having your wife/husband at the table isn’t a profound enough deterrent to keep one from flirting with another’s spouse, then one needs to thoroughly examine the mettle of one’s marriage.
As with any social event–including ones that are just men or just women–there is a degree of common sense that must go into who is invited. Nobody wants that one man who’s going to drink too much and do/say inappropriate things, and no-one wants the married woman who shamelessly flirts with other men at the table. If people are known to behave in such a manner, don’t invite them.