I would appreciate input from locals or anyone who has done a self-drive Ireland on this proposed itinerary. I will have already visited Dublin the previous week without a car. I will be driving on my own. Mon. 28 March: pick up rental car at noon and drive to Cashel. See what I can that afternoon and stay overnight with time in morning to see additional sights if needed. Tues., 29 March: Drive to Killarney with stops in Adare village and/or Lough Gur heritage site. Stay over 2 nights . Wed., 30 March: Drive the Ring of Kerry. Thurs., 31 March: Drive to Cliffs of Mohrer via Tarbet-Killimer ferry route. Drive to Burren National Park and then to Doolin for overnight stay . Fri., 1 April: Drive to Galway. Stay two nights. Sat. 2 April: Ferry day trip to Inis Mor (Aran Islands). Sun,, 3 April: . If not drive through Connemara or ? Mon. 4 April: ? Tues., 5 April: Stop at Newgrange/Knowth on way back towards Dublin. Need to return rental car by 5 pm. Overnighting at hotel near airport. Any advice greatly appreciated as this is my first trip to Ireland.
Consider renting the car right away upon landing and then spending your final week in Dublin. This will give you an additional night to add somewhere else. Cashel is a pretty dreary town, Rick would call it "workaday". The castle is absolutely beautiful when lit up at night, but the city itself is not worth the overnight stay. Consider Kilkenny instead and visit Cashel on the way to Killarney
There's really nothing else to see in Cashel except the Rock. If you watch the introductory film (and you should), then wander around, you might spend a couple of hours there all told. We spent the night in Cashel at a sheep farm just outside of town (Rahard Lodge). There were brand new lambs at the time (early April) which they let our kids hold. Just down the road toward Cork is Cahir, which has its own castle which sits in the middle of the Suir River. It's well worth a stop if you are headed that way at all. Personally, I wouldn't bother with Kilkenny, as the previous poster suggested. I think your plan looks pretty good as it is.