For scenic attractions these are some of the best places to visit; Wicklow Mountains National Park, The Boyne Valley, Cliffs of Moher and the Ring of Kerry <insert joke here>
Galway and Cork are great for cultural events like festivals and the likes, Dublin has all the decent museums and art galleries etc but is pricey enough and filled with Dubs
If they fancy just getting pissed for a week just tell them to go to Galway and I'll look after them