The Dingle Peninsula is my bolt hole from London. I own a cottage on the North side - across the Conor Pass from Dingle. It's a fabulous place and there's music to be found everywhere.
My favourite session of the week is Saturday night in Brandon at Tig a Cuinne (The Corner House). It's largely the same locals each week augmented by the regular tourists (such as me). This is an out of the way place that is on a dead-end so does not get masses of tourists. The session can start late and continue until much later! **I hope there's no Gardai on Mudcat**.
O'Connor's and Tig Tomsi's in Cloghane, my village, have paid musicians regularly - they put up a sign outside to say if there's anything on that night.
Impromtu sessions can happen anytime there's any excuse at all. A stranger walking in with an instrument is often enough! Dick Mac's and O'Flaherty's are well worth a visit but try also An Drochead Beag and a wonderful little bar down by the pier called P.Moriarty. This bar has family connections to the dark-haired temptress in Raglan Road - I've never heard music in there but it'll take you back to what bars used to be.
Have a great time. I'm over myself for the two weeks each side of Easter weekend.