I know that you’re in the itinerary planning stage, but are your flights actually booked? The reason I’m asking is because I wonder if flying roundtrip to/from Dublin would be cheaper than flying in to Shannon and out of Dublin?
And then, are you planning on getting off your plane (at whichever airport) and immediately hopping into a rental car and driving (on the left side of the road) to Galway? Or reaching Galway by bus or other means, and then getting a car there? Or is this trip skipping a rental car entirely, which would make your itinerary more of a challenge?
Anyway, IF you were to fly to Dublin and catch a comfortable CityLink bus directly from the airport to Galway, you’d be in Galway in 2 1/2 hours, just a bit longer than if you flew in to Shannon. We did that, sat on the top level of the double-decker bus for a scenic view of the countryside and also a little nap after a long flight, and were in Galway before we knew it. We got our rental car (from Enterprise) the day we were departing Galway. Unless you had specific reasons for Shannon, such as stopping in Ennis on the way to Galway, Dublin would be worth considering.
Ok, so if you wanted to get in both the Cliffs of Moher and Skellig Michael, I have a suggestion for a couple of tweaks to the tentative plan you mentioned above.
After your one night in Galway, head to Dingle, stopping at the Cliffs of Moher Experience visitor center along the way. You can see the Cliffs up close, from the top, and viewing them at an angle in the distance from the visitor center.
Get in two nights in Dingle. If Doolin would have been partly for the music, you’ll still have great music opportunities in Dingle, and you’ll appreciate having two nights there. When we were in Dingle way back in 2012, boat Captain Des Lavelle ran trips to Skellig Michael from Dingle, but not anymore. The vast majority of Skellig trips now leave from Portmagee. There is one boat we used in 2023 that departs from Derrynane, but that’s even farther south than Portmagee. So, you’d want to head south from Dingle for your next night.
As noted above, Cahersiveen is a good overnight town for potentially reaching Skellig Michael the next morning. Trying to make your Skellig boat if driving from Dingle would require leaving Dingle really early in the morning. From Cahersiveen on Skellig Day, it’s a short drive to Knightstown, then the very short car ferry to Valentina Island, then drive to the harbor at Portmagee for your pre-booked Skellig boat. Or, stay on Valentia Island instead of in Cahersiveen. Or, stay in Portmagee. Check lodging availability and prices.
There are two types of Skellig boat trips. Landing boats take you to Skellig Michael (depending on how rough the seas are), for hiking the 600+ steps to the top. Boats can get cancelled the morning of the scheduled trip, if water’s too rough to moor at Skellig Michael for disembarking. There are also “Eco” boat trips. which usually still sail even when the water’s too rough for landing on the island, and they sail around both Skellig Michael and Little Skellig islands, without landing.
From here, return to your itinerary with Kenmare or Killarney (1 night).