So, I don't even know why I tried this in the first place, but I found a way to avoid having your dwarves throwing parties all the time..!
I haven't tested with versions prior to 0.31.04, but I'm pretty sure it would work with other versions just fine.
So I started a fort last night and it's a year in. Zero parties. Several dwarves got married but none had any formal celebrations. I no longer need to go out of my way freeing and re-assigning zones to get work done.
The trick? Create your rooms normally, but never activate the Meeting Hall (Y/N) option. Instead, use the "i" zone tool to designate a meeting hall over areas. Apparently dwarves need a zone designed as a meeting hall attached to an object to throw a party, as hinted by the "Urist McBum organised a party at Gold Statue." announcement.
You still get thoughts from dwarves going to the areas, admiring the furniture or eating in a legendary dining hall, but no parties, ever!
Oh and if you're annoyed because you can't shape the zones perfectly on top of a room like you would when going from the furniture's menu, well, you can. Just make it bigger than the room you want to designate over and then chip away everything you don't want by removing only part of the zone. Voilą, no parties, and only one zone covers your room perfectly.