I'm really happy for you and your friends, Athur. Use this word to your heart's content. But for me it just doesn't meet the standards of a successful portmanteau, which I think of as the "chortle standards" in honor of one of the best portmanteaux ever coined (by Charles L. Dodgson no less): clarity of origin (snort and chuckle), simplicity or elegance of meaning derived from the original components (a chuckle that is like a snort, or vice versa), ease of use (easily pronounced, easily inflected - chortling, chortled), and usefulness (a particular kind of laugh that until chortle came along had not been aptly named). So go ahead and have your menfauxpause, but don't expect me to chortle along with you and your word-coining associates, though I might be chortling at you.
I quite agree rolig; it's your last objection that really makes this word an utter failure. You can't just stitch together any two words and have a witty portmanteau - there has to be a verbal vetting, too.
This word annoys me in so many ways I don't know where to begin. For one thing, its relation with two of its three component words – faux pas, and menopause – is virtually opaque when pronounced (and it is not easy to pronounce). Second, since the key component word, menopause, is a term that primarily refers to women's biology, it is not even clear that the men- part of this portmanteau references men (the usual element in such things is "man-"), so perhaps this is something inappropriate that women do during menopause: a menfauxpause. Why not? Third, is this a singular or plural word, or both? Who knows? The last two syllables sound like the non-standard plural pronunciation (by some) of faux pas, and yet it looks like a singular noun. And fourth, since the first syllable of faux pas is normally not reduced, but the second syllable of menopause almost always is reduced, there is no easy way to say this word that would clearly relate to both faux pas and menopause at the same time. This is not a successful portmanteau, however clever it might seem at first glance.