The hotel in portumna, Tipperary (can't remember name) is v. nice although not a lot to do around there. We've been on four or five of these breaks and this hotel is one of the best we stayed in - a little bit above the average three star.
Blarney park in Cork is good - nice swimming pool - great for kids.
Brandon hotel in New Ross- wexford has a great pool area as well (not much to do in New Ross itself though)