Sile, feel free to chime in! Here's a thought on exhibition strategy:
SIRIUS -- I was involved with hanging one photo exhibit there and the space is WONDERFUL!! It's a gorgeous old building with beautiful wood floors, lots of light, very "airy," and right on the water with restaurants and shopping close by. The "Queenstown Museum" is also close at hand and a lovely hotel nearby as well. A year ago, the manager was an American lady who was an enthusiastic film photographer herself, but I do not have her contact info now. Should be easy enough to find her, though. I am confident she would be most receptive to discussing your ideas.
If you have Airfield (very doable, it seems, with Peter's and Fintan's connections) in Dublin, and Sirius in Cobh (or the Cork Museum, but they may have a longer booking advance time), you could reach two areas of the country, reach lots of young people (students who might convert to film!), and give all your members good excuses to get together on two different occasions. If you do the first exhibit in Cobh, they are well-wired for publicity so if you're lucky, you'll probably generate some mentions in at least one of the "Big Three" Irish papers, as well as smaller ones. "The Examiner," for sure, should give you some publicity, but you may make the Dublin papers as well. "Rebellion Against Digital" has a certain news appeal that might prick the interest of culture and art writers.
With that exhibition behind you, move to Dublin for the Airfield venue. With the publicity you will (hopefully!) have already generated from Cobh/Cork, it will be easier to garner attention in the Dublin area and you might even get Kodak or Ilford or Fuji to throw a little sponsorship money at you. Even 1000 Euros would be enough to make a nice pamphlet extolling the virtues of film, APUG, have some bios and info on the exhibitors, etc.
Incidentally, there is a company in Ireland (forget the name) that makes nice, wood frames for photos and they're not expensive. Not archival, of course, but they look nice and would be perfect for your exhibition. Seems to me they're in Cork, but can't remember for sure. They might be willing to donate frames for your exhibition (40 frames at 20 Euros each adds up!) in return for being a named sponsor and getting a little publicity out of it.
You might want to consider standardizing the size of the mats, but not necessarily the prints. It's much easier to do the framing if all the mats are the same size and it's cool to have different sized prints within consistently-sized mats and frames. It will also be a lot easier to get the framing company (a sponsor!) to donate off-the-shelf frames in mass-produced sizes. Something to think about . . . .
As for number of prints, you might want to do a quick tally of possible exhibitors to see how many there will be and then challenge everyone to do two or three (or whatever) prints so you can estimate a final number of prints. I know Sirius in its two gallery rooms can easily hang 40+ 16"x20" frames and assumedly Airfield could match or better that.
Oh to be in Ireland right now working with you guys on this!