Good idea to start a new thread since the dates have changed. :)
I think it sounds like a wonderful plan to stay in Doolin, Killarney and Dublin for 5 days each, and explore the area from there! The locations have so much to see and do, so there is a lot to choose from.
Take a look at some of the day trip options for:
I have also collected some personal suggestions for you in this scrapbook
. If you create an account you can add more articles that catch your eye, as well as share it with your travel companions. :)
I hope you'll receive more tips, suggestions and ideas from our other members, and please don't hesitate to give me a shout if you need anything.