Armies around the world utilize the same effect to foster a feeling of unison through repeated drills:

Words are inadequate to describe the emotion aroused by the prolonged movement in unison that drilling involved. A sense of pervasive well-being is what I recall; more specifically, a strange sense of personal enlargement; a sort of swelling out, becoming bigger than life, thanks to participation in collective ritual. (McNeill 1995, quoted in Kesebir 2011)

I'll counter a personal anecdote with a personal anecdote: I've been to the military, and though drilling can foster group bonding, it did so at the expense of the activity itself. Marching around the plaza or dashing around in the woods was the common enemy that most everyone hated. It works if the law requires you all to do it, but doing stuff people hate probably won't work for a voluntary assembly.

Synchronized actions may be good for building a sense of communality, and a particular activity may be a synchronized action, but there are still going to be people who don't like it; I'd much rather play board games than sing or dance. I'm unlikely to be attending any meetups, but I imagine the best thing to do (at least for a first meeting) would be to simply ask the people what they want to do (in advance, of course). Get the people together first and don't set to work on saving the world until a couple of conventions down the line, as it were.