Hi Mary,
Take into account, The Ring of Kerry is around a 7 hour round trip from Ennis. Moving your home-base to Killarney as you suggested, would cut down a lot of your travelling time, and you could see Killarney National Park, Ring of Kerry and even Dingle. It means you could see more during your stay as it's very accessible to a lot of tourist spots.
There are also a lot of companies offering day trips based out of Killarney to the other places you want to visit like the Cliffs of Moher and Ballina. You can check some of them out
here. If you want to hire a driver, there is also a company in Killarney who offer that service, you can find them
here.
Let us know if you have any more questions!
-Cathaoir