Despite my comments about driving, stifle's post is spot on and reflects a great alternate way to see Ireland (and many other European countries, for that matter). Although I prefer to drive and don't find driving "on the other side" at all intimidating, your feelings about driving in Ireland are probably going to be directly proportional to how you feel about driving in the US. I like being behind the wheel of a car so I rent most places I go; my youngest sister hates driving, and other than taking the occasional ride as a passenger when we're in the same country at the same time, takes trains and other public transport. I've had a great time on my trips, but so has my sister.

Keep in mind that the distances tend to be shorter than in the US while the roads and driving customs are foreign to you. I'd check the pricing on trains to see if they make sense to you. And, although you might give up some of the rural sights, such as some castles, that you might want to visit, you might still find some tours that will run you out to a nearby castle or dramatic site that you might wish to see.

I guess just another way of getting you to do some more research so that you can plan a trip that you and your wife will enjoy.