I'll also recommend Tom Coyne's book; however, it might be even better to read it AFTER you return. Since Coyne walked around the country it probably doesn't offer that much advice for a first timer. Maybe more enjoyable to read later and relive your experiences.
I hope that your opening round at Royal County Down doesn't spoil you for the rest of the trip. RCD is truly the best course I've ever played; however, the food and selection of restaurants in Newcastle is abysmal. It will improve throughout the rest of your trip!
Currently, there are some tremendous deals in airfares, lodging and greens fees throughout Ireland. I'm not sure whether your courses are already set in stone but there are a couple of particularly good deals that I've seen recently:
--2 for 1 greens fees at Ballybunion Old and Cashen if played within a 7 day period;
--bundled and reduced greens fees for Ballybunion (Old), Tralee and Waterville; and
--reduced greens fees and lodging for two rounds/two nights at Ballyliffin.
Lahinch-- consider staying at Lahinch Golf & Leisure Hotel. Easy walk to the course. Particularly good food and friendly pub in the Marine Hotel right along the main drag in town.
Waterville-- stay and enjoy the coziness and views from the upstairs clubhouse bar. On your way home, stop at Nick's in Killorglin for a wonderful meal and great piano bar/restaurant... which brings up another extremely important point. Be VERY VERY careful drinking and driving. In fact, just DON'T do it. The laws are very strict. Plus the roads and directions are tough enough already!?
Finally, enjoy Kinsale. I think it's the nicest town in Ireland. Picturesque harbor town (stay with Maeve at the Blindgate House) with excellent restaurants (Toddy's, Man Friday, and Jim Edwards just to name a few). Plus the food at the Old Head clubhouse is excellent also!).
Enjoy! I'm jealous...