Car Rental Questions

whatever you do, do NOT use a car in Dublin. Rent at the airport on your way out of Dublin and drop off at the airport on your way back in.

I'll second Sharon. Do not drive in Dublin!

Definitely check to see if your hotel offers a shuttle ride from the airport--if not, take a cab, especially if you're in a group. It's worth the extra euros to have a direct ride to the hotel and not to schlep your bags from the public transit stop.

Do not drive in Dublin (or anywhere in Ireland) if you are a timid driver. My husband loved the experience, but I was terrified every time I set foot in the vehicle. The roads in the villages are very narrow and locals drive very fast. Dublin felt like any other major metropolitan area, with locals driving confidently and fast. It was not easy to navigate by car. Parking was also difficult to come by. Our daughter was studying there and we could not get a hotel near her school, so we drove back and forth across the city during our visit. Once we mastered our route, it was manageable, but I cannot stress enough that the drivers are aggressive (my husband fit right in).

There is another way. Why not take advantage of the train system and do a one-way rental from Dublin airport to Kilkenny, drop the car there, then train from there directly back into Dublin? That way you wouldn't have to go anywhere near Dublin city traffic and would arrive near the city center at Heuston station...a short taxi ride to your hotel. Would simplify the logistics of having to drop at the airport and then proceed into the city too.
Although I agree with the advice to avoid driving in Dublin, driving in the countryside is a pure joy despite some of the narrow rural roads you may encounter. The National roads (N roads) are modern, two lane thoroughfares not unlike the roads you drive on at home. It's true that many of the rural roads aren't wide enough for two cars to pass side by side, which just means that you have to be aware of the local rules of the road...requiring one vehicle to pull over into one of the pullouts to allow the other to pass. People (locals and tourists) manage to do this every day without too much drama, and you'll no doubt get the hang of it pretty quickly...there's not that much of a learning curve. That's not to say that your heart rate won't spike a few times in the early going, but Irish drivers are some of the most patient and understanding you'll encounter anywhere. Fact is, in the time it took me to stop and begin to figure out what the heck I was supposed to do, the approaching driver had already pulled over and was waving me thru. It's really not that big of a deal.
Read thru some of the discussion threads on this forum dealing with driving in Ireland - some pretty good advice to be had. Rent an automatic, study the Google maps street view to preview your routing each day, slow down, go with the flow and you'll do fine.

I would definitely fly into and out of Shannon. The rental car becomes an easy matter from Shannon.
It's easy to get used to the driving on left when starting in Shannon. I've been to Ireland many times and just love driving on the left. It will only take a couple hours to get your bearings. Have fun and enjoy. No matter where you go, you will see the beauty in the country and will begin to make plans for your next visit. I'll be there again in June as well! Make sure that you get total rental cost with all insurances (including glass and tires) if you want to be fully covered.