Southern Ireland Iterinary Help!

Cork to Dingle to Kilkenny in one day will take 6+ hours with no time to see anything. Dingle is a wonderful spot but it is a long way from everything else. Might be worth it if you stay in Dingle on Thursday, then back to Kilkenny on Friday? Still a lot of driving.

You only have two nights and distances are vast in Ireland. Remember, you’re driving a car with a steering wheel on the opposite side than what you are use to and driving on the left instead of the right. Expect it to take longer than what Google maps show. Pick either Dingle and the peninsula or Kinsale / Cork.

I agree. You'll be spending much of your time in the car. Driving takes longer than one would expect looking at google maps---road conditions, moving sheep, unexpected stops of interest, etc.

It sounds as if Cork/Kinsale and Dingle are priorities (over Adare, Rock of Cashel or Kinmare...) so forget trying to add anything else. You will barely have time to see much in either location with your limited time.
By all means, don't drive all the way to Dingle only to head back to Kilkenny in the same day. Either skip Dingle, or stay overnight. There is so much more to the Peninsula and town than what you can do in a day. I would be on the road at daylight to Cork, spend a few hours there (depending on the draw) and consider getting to Dingle, or closer, that night. You will have limited daylight hours, however, so perhaps an early morning drive to Dingle.

Enjoy!!

Edit: LOL I took too long to submit...I see we're all on the same wavelength.

SLOW DOWN! As other have said that is an ambitious itinerary, unless you want to spend long hours in the car. You are going to effectively lose most of Wednesday travelling to wher you bwant to be and most of Friday travelling back to dublin reaqdy for the flight back on Saturday afternoon. Depending on what time you have to check in, make sure the last overnight isn't too far to drive from Dublin Airport.
Rather than hare around trying to see both Cork/Kinsale and also Dingle, think about just choosing one place for those days and explore the area properly. There's plenty to do and see in either.

Rock of Cashel can be done from Killkenny on the way to where ever on the Wednesday. (Adare is getting mixed reports - have a read here - and a lot of posters are saying it doesn't live up to the hype. Skip this.)

I'd recommend choosing one place, as others have mentioned. If you have an enthusiastic "wrong-side" driver, then I would choose either Dingle, Killarney or Kenmare and stay all three nights. Weds: Rock of Cashel on the way. Thurs: Ring of Kerry or Slea Head drive or Beara Penninsula, depending on which base you chose. Fri: the other drive or, if you're in Killarney, choose one of the local activities. Sat: turn in the car (in Killarney?) and take the train back to Dublin. If you can fly home from Shannon, all the better, or fly from Kerry Airport to Dublin. If you don't have an enthusiastic driver (or if your driver wisely wants to see the scenery), you can do an organized tour of Ring of Kerry and/or Dingle from Killarney or a tour of Dingle from Dingle.
It's a lot of time in the car, but this is the scenery people want to see in Ireland. Cork doesn't have that.
If you want iconic scenery with less time in the car, go to Doolin (or Galway, I guess) to visit the Cliffs of Moher and the Aran Islands. Return time to Dublin will be much shorter. Again, fly home from Shannon if possible.