If you're flying out of Dublin you're going to be in heaven! The whiskey section in the airport is gigantic, and has many, many local Irish brands! Glendalough, Writer's Tears, Dingle...... there are many! If you want REALLY good Middleton has a great rep - I've just never spent more than 30 on a glass of whisky and I'm not starting now! ;-) It's very "dear" as they say, here.
I'm not sure about Shannon but my neighbor flies through there alot. I do know that it is much, much, much smaller than Dublin so I doubt they have a place as big.
Speaking of Dublin Airport -- if you have a bit of time, Marqette restaurant has an amazing area. They buy local Irish produce, they have organics, they have rush items and take your time items, and this past year won BEST AIRPORT CAFE IN THE WORLD!!! I have a layover there Monday, I'll beeline right to Marqette! (flying Kerry Airport to Dublin to Heathrow to Dulles..... sigh.....)
Expat living in Ireland