Bed & Breakfast recs for Kilkenny & rental car ?

The transition to a righthand drive and driving on the left is easier if you're not jetlagged the moment you step into the car. Will you have a chance to acclimate for a day or two before picking up your rental? The other issue you might encounter is that most rental cars are manual shift, and even in the same make and model renting a car with an automatic transmission adds significantly to the rental cost. It's not a difficult transition to shift left-handed but if manual transmission intimidates you you'll want to make sure to request and pay for an automatic. Another bit of advice is that most credit cards except for some MasterCards do not provide CDW coverage for Ireland rentals so budget for the insurance. Our travel insurance nominally covers rental car damage and theft but only for damage "outside of my control" so I pay for the CDW in Ireland.

Ireland's rail network is mostly a Dublin-based hub&spoke, and doesn't get to many of the scenic areas so you'll be better off with a car. Where else do you plan to go during your trip?

We relied heavily on Google Maps, TripAdvisor and booking.com to identify and prioritize B&Bs with availability for our dates, but where possible we book directly with the property. It saves their costs a bit and often they give a perk like a free breakfast that might cost someone who booked via a reservation site 5 or 10€.

For what it's worth, in Kilkenny we ended up a couple of miles out of town at the Newlands Country House, http://www.newlandscountryhouse.com . It was fine, met our budget and availability need, but we did need a car to really enjoy this location as it's definitely in the country. If you won't have a car or will prefer not to drive to dinner and the sights you'll need something in town.

Hi, Caroline!
We were in Ireland this past May. We rented a car but, although being used to manual shift but not used to driving on the other side of the car & road, we opted for an automatic. It was a good decision. Driving on the other side was not as difficult as dealing with the narrowness of the roads.
Anyway, in Kilkenny we stayed at and would highly recommend Twin Oaks B&B. It is out of town but not too far if you have a car. They had probably one of the nicest rooms of our 3 week stay, the facilities were comfortable and pleasant, the owners were friendly and helpful, and the breakfasts very nice.

Hope that helps.
Have fun!

Definitely book the car ahead of time, especially if you get an automatic transmission.

As for Kilkenny, with a car you might want to check out the Pembroke Hotel, a 5-minute walk from the castle with off-the-street parking. It was a really nice hotel with great wifi, comfy beds and amenities, and the price was equivalent with most of the B&Bs we stayed at. There was a great restaurant for dinner just down the road, a nice pub across the street, and a convenient pharmacy on the corner for when your mom has a cold and needs cough medicine. They did have a decent breakfast on site, as well.

Very good advice from the other posters. Would only add that springing for a car with automatic transmission really is the way to go if this is your first time - will save you a lot of stress as you negotiate the learning curve for driving on the left. More expensive, but worth it for the peace of mind.
Driving in the countryside is a pleasure - driving in the cities not so much...avoid it if you can by picking up and dropping your vehicle outside the city centers - the airport is an obvious starting point, plus the airport operations typically have a larger and better selection of vehicles, ensuring (hopefully) that the automatic you've booked will actually be available when you arrive.
To help learn the sight picture for LH driving, as well as to preview my daily routes (to view intersections, roundabouts, signage, etc) , I've used the Google Maps street view feature. The level of detail, even on some of the rural roads, is quite good. Helped me a lot. Might work for you too.