My report back:
Stayed in Malahide (North of Dublin and just a tad north of the airport) at the Grand Hotel Malahide for start and end of trip. Great location. Can take a DART train right into city center and the suburb is pretty and has some nice pubs and close to Howth. The hotel was basic but had a fun health club and so I took a sauna with the local lads each night we were there. Good place to stay because good warmup drive from airport.
Drove to Kikenny (wife drove - my job was to tell her every 10 minutes that she was going to hit a curb) but mostly big moterway.Stayed at the Mount Juliet Estate - a golf resort and it may be the best all around hotel I have ever stayed. A bit of a way from Kilkenny but an easy drive. The hotel grounds had great walking paths as well and a good steam room to steam out the Guiness. The town was crawling with Purdue folks who were there for a pre-St. Pats parade which ultimately got cancelled.
Thence to Killarney and a stay at the Cahernane House. Fantastic all around. Could walk to town and National Park just a couple of kilomters away. Really liked the town and the accessiblity to all around Killarney and Ring of Kerry. We actually didn't drive down into the smaller roads that led down to the water in the area but that would have just taken some patience and a few deep breaths.
I'm glad we didn't do a tour. The hotels we stayed at apart from Grand Hotel Malahide (which was still very very nice) were pretty damn high end -- if it were me I probably would have economized on that and just ate pub food. But the people were so helpful that we enjoyed our own pace and just going to sites based on local recommendations.
If I did it again I might do something like try to get to Galway by train or bus and then rent a car there rather than drive the whole country, but if the car price doesn't bother you, I thought the car made sense. The bus and train schedules and routes to me weren't very convenient when I looked closely at them.
The weather looked scary on paper when we were planning for mid March but once there it was perfect -- a bit of rain every day, wet, but sun peaking in now and then. Waterproof light hiking shoes, travel pants, fleece top, beenie and raincoat did the trick.
Lovely. Grand.