Thank you, Timothy--I knew you'd be up to the challenge!
You are more well-read in the area than I am, and I look forward to browsing Amazon for your titles. My shelves contain these books:
"The Celtic Way" by Ian Bradley
"Thin Places" by Tracy Balzer
"The Celtic Way of Prayer" by Esther de Waal
I think you'd also enjoy "The Celtic Way of Evangelism" by George Hunter of Asbury Seminary. And although not specifically in the genre of Celtic spirituality, Thomas Cahill's "How the Irish Saved Civilization" is a go-to book for anyone interested in the connections between ancient Irish spiritual and literary life.
As for traveling to Ireland: My wife and I went on a packaged group tour offered through our travel agent. We flew into Dublin (where the airport is designed along the same lines as a Rubiks Cube) and stayed there for only a day or so before traveling near the southern coast and ending up in Killarney, where we stayed for a few days, touring the Ring of Kerry, the Cliffs of Moher, and other well-known sites. We then went north and stayed for a couple of nights in the coastal town of Westport before heading east back to Dublin. Most of the really breathtaking scenery and the small-village charm is to be found on or near the west coast, so if you want that you'll definitely have to go to the opposite side of the country from Dublin. I think the packaged tour was a good choice for us, since it gave us the opportunity to see a lot in a short time--plus, we had the voice of a very knowledgeable (and entertaining) driver and guide who helped interpret what it was we were seeing. But at the same time the tour didn't seem rushed--we had plenty of opportunities to walk the streets and explore on our own.
That said, if we ever go back I think we'll travel sans guide--we've talked about spending a week in Killarney in a B&B and going on some walking tours of the area. One of my favorite memories is going into a Killarney pub one evening where there was a music session going on--guitar, fiddle, maybe a button accordion--and a little girl of about 6 (evidently the daughter of a regular patron) was step dancing to the music.
Slàinte!