We will be driving from Dublin to Kinsale at the beginning of our trip through Ireland (after spending 3 days in Dublin) and we need to arrive in Kinsale by 6:00pm. Originally, I planned on driving the inland route, stopping at the Rock of Cashel. However, a friend who lived in Ireland said it would be more interesting to drive along the coast through Wicklow and Enniscorthy with a side trip to Glendalough.
My concern is that this will be our first day of driving -- getting accustomed to the left side and the other unique customs of driving in Ireland. My wife and I are in our 70's and frankly, are a little slower to adapt to change than we used to be.
Is this route really worth it? Will it be more difficult for a novice driver? How long will it take? (If we have to drive non-stop because of the distance without time to stop and enjoy, it's not worth it.) On the other hand, we would like to see as much as we "reasonably" can.
I have been to Dublin, Wicklow, Glendalough, Cashel and close to Kinsale; I have not visited Enniscorthy. You have a choice between Cashel and Glendalough/Enniscorthy/Wicklow on the way to Kinsale.
I have seen Cashel twice and Glendalough three times. Each is an excellent choice, and you cannot go wrong with either. Having said that, the setting of Glendalough -- rolling hills, glacial lakes, forests -- is a bit more picturesque than Cashel, which is a set on flat country spectacular in its own right. The antiquities of the two sites are equal in their majesty and historic worth.
However, you will be new to driving in Ireland. I have driven twice in Ireland, once with a stick shift. I definitely had to keep my wits about me driving on the left side of the road, where left turns are easy and right turns hard. In Glendalough, you would be driving in semi-mountainous and narrow roads. I drove in the Wicklow Mountains but was on high alert. The drive to Cashel and then onto Kinsale is a bit easier because it's mostly flat.
I believe the drive to Cork, which is near Kinsale, took me four hours. If you add a stop in Cashel, that would add a two hours. Glendalough will add probably 2.5 to 3 hours.
I suggest getting as early a start as you can reasonably manage and picking up your car at the airport - the concessions there have the largest fleet of rental cars in the country so you'll have the best chance of getting exactly the type of vehicle you want, particularly one with automatic transmission which will simplify things for you quite a bit. The airport concessions are also open early (around 5:30 in some cases) as opposed to those in the city which typically don't open until 9:30 or so.
The Old Military Road (the R115 on the map) is an especially picturesque way to go, and early in the morning you'll have it virtually all to yourselves as you head down to Glendalough. An early arrival at the monastic site would get you there well before the tour buses arrive and the crowds start to roll in at 9:30.
Driving the Motorway from the airport and then the R115 from there would be an easy introduction to driving on the left for you I think. I recommend using the Street View feature on Google Maps to preview sections of the route you'll be driving - always helps me and I've done this quite a few times.
From Glendalough I'd suggest turning inland to pick up the Motorway down to Cashel for lunch and a tour, then on to Kinsale from there. I do think Cashel is worth seeing and it would, after all, be a natural stopping off point on your trip south.
That route, coupled with an early start, will easily get you to Kinsale by 6 PM even with the stops at Glendalough and Cashel.