Looks like it's about a 20 min drive from The Cahernane House
It's less than a 20 min walk or 5 min drive from Cahernane (1.3 km/< 1 mile)
This company rents horse/carriages ("Jaunting Cars") to explore the Killarney National Park. They also offer boat cruises and other tour options. We will likely be doing the Lily of Killarney lake tour on Sunday.
This incredible feature is about a 2 h 40 min drive from Killarney (187 km/~116 miles)
The Book of Kells is located in the Old Library on the University of Dublin Trinity College campus. You can buy a "30 min" ticket for entry into the Old Library and to virew the book. Tickets are €18.50 (~$20).