I'll be working at an Irish bar on Paddy's Day and I agree that finding a space, public or "back room" that is not a total madhouse is a near certain impossibility. In my experience, the food is crap, the beer is poured too quickly (for Guinness), the waitstaff are harried beyond belief, and I love every minute of it:)
It's just not the day to go out with a group and expect to be able to converse or even hear each other. That said, if you do decide to do a private party, let me know and I will make up some mix cd's for you. I have an extensive -some might say obsessive- collection of Irish music. Pick a theme, trad, rocking, Scottish, I can do it.