How long would this take? What route would you take? Do you need to backtrack? Could you do Kinvarra castle dinner the same night?
The drive from Galway to the Cliffs of Moher will be about 2 hours. From the cliffs, it's just over an hour or so back to Kinvarra. And yes, you will be backtracking. You can go to www.viamichelin.com and put in your starting and ending point to see the route (add 25% to their time estimates, though).