All, good points, esp the part about B&Bs but I would maybe look at the Dingle peninsula instead of the Ring of Kerry, especially given the time frame you are going (peak\near peak tourism). Lots of tour buses on Kerry but I don't remember seeing a single one on our trips west of Dingle (other than the small ~8 person vans). Less cars and tourists in general as well. The scenery is just as good (IMO its better but I hate traffic so I might be biased)

I've found http://www.theaa.com/route-planner/index.jsp to be fairly accurate in terms of time even in the countryside. I add about 10% on to the trip time and slightly over exagerate on the time for lunch (I leave an hour but it usually takes us less). Those together have really only failed us in our Isles trips when we stayed at a sight longer than planned and ended up in the snarls of rush hour traffic

Now that said I have spent many weeks driving Ireland, Scotland and England. My wife has not spent nearly as much time driving there and it took a bit for her to get comfortable the last time so her sections were much longer.

"How far are we now?" she asks as shes driving
"About 30 minutes away."
"But we were supposed to be there already!"
"Yes but we were also supposed to be going twice as fast."