Mum of 2.
Right there, that is why you don't play with matches.
It is very rare for ...."and then across the crowded room, 2 quasi strangers, yet our eyes locked and passion billowed out of our respective knickers in an instant"... infidelities to happen. Typically at some point there was some banter, a little "harmless" flirting, a gradual pushing back of the boundaries. A vast array of red flags very carefully ignored to allow people to lie to themselves that it was all beyond their control.
Unless your marriage is made of cast iron, placed on a foundation of titanium, and\or your husband is not particularly fussed about what you get up to with anybody else, the safest plan is to walk away as soon as the first flutters start. Because it is very, very, very easy and doable in comparison then, with no harm done.
If you continue to put yourself in a context where flirting takes place then make no mistake about it, whatever happens later on down the line is NOT an accident. You quite deliberately chose it, giving little weight to the undeniable knowledge that you were gambling with other people's feelings and future.
If you can't walk away from this then please never declare "I'd die for my children", because if you can't even make the far smaller sacrifice of avoiding taking a needless risk with their stability and tranquility within family unit, then claims about the larger just looks like delusional hyperbole.