After a much regretted 4 night stay in Killarney during our first trip years ago we've starting staying along the corridor between Glenbeigh and Castlemaine, which we find avoids the traffic congestion in and around Killarney town while still permitting easy day trips to explore Dingle, the National Park, the very pretty Gap of Dunloe, and the northern half of the ROK in general.
We like to unpack once and be done with it for several days rather than constantly moving around.
We've always had good luck using booking.com when searching for accommodations. Their filters are helpful in quickly narrowing things down according to our particular interests, and we've generally found the reviews to be pretty trustworthy.
If you'll be coming from Dublin, be aware that there are a couple of flights per day to the Kerry airport that would save you the long drive across the country. There are a number of rental car outlets located at the airport.