here's the best advice you've had yet... forget the north of ireland (county down, portrush, castlerock, portstewart, ballyliffin) unless you can get a direct flight to belfast... also forget the west / north west (enniscrone, county sligo, donegal, rosappena, carne, connemara) because they are too far away from an airport and some hefty drives...
to shorten your flight time, go for the south west (ballybunion, tralee, waterville, lahinch, doonbeg) flying to shannon... almost all dublin flights have to land at shannon first anyway before taking off again for dublin... there are some lengthy drives with this itinerary as well though...
alternatively add on a bit of flight time to dublin and stay near the airport where you are in striking distance of portmarnock, the island, baltray, royal dublin or seapoint and not that far away from co. down with the new road.... you could also travel south to the european and risk the dublin traffic but why bother...
in short: south-west equals shorter flight but more driving... dublin equals longer flight plus less driving (theoretically)