We have done a couple of small M&Gs ourselves when we were traveling to bigger cities where we invited a handful of couples we were interested in meeting to meet up at a nice hotel bar. Both of those worked well with one couple not showing up for each (20% fail rate) and a couple or two who elected not to play at each. The remaining two or three couples all joined us on our room both times for some fun.
We have attended a few larger M&Gs held in a private party room at a local bar/restaurant. The ones like that we have attended typically had 20-50 people, but of course no place to play on site, so truly more of a "M&G only" with couples exchanging contact info with those they hit it off with for later private meet ups.

