Hi we did it in 2004.  My husband drove from Shannon airport to Dublin.  We had a small car but not small enough.  The roads were so narrow and driving on the wrong side and roundabout crazy.  The windshield wipers going and trying to find where to stay.  I would definitely make reservation and have a good map to find the places.  They were ok the B&b's.  Be sure to get the car insurance and take pictures of your cars before leaving.  You have to pay extra for other people to drive so my husband did it all.  We did not drive at night because of the glare of the car lights and oh yes the YELLOW Line down the middle of our roads in the U.S. runs along the outer edges and the white line is in the middle of the road.  We had no children with us.  Everything was very expensive but I am ready to go back again.  We had a great time.  Caroleann Quan