Jeff,
Dingle is a lovely little spot and Connemara is nice but Bleak!Kinsale is a great place for a break, depending which way you come from Dingle you might pass a little village called Annascaul,birthplace of one of my heroes, a guy called
Tom Crean .I have been to his South Pole Inn and very drunk they made me!
Waterford is a great spot,cleaner than Dublin and easy to get around on foot,pity Kilkenny is next door

Just across the river Suir actually,where the Tall Ships set sail from on the first leg of their race.
September is generally better weather wise then June here,should be good as this year so far has been fine and warm for a change.
Only thing you may find is we all use the Euro currency now and apparently Ireland is one of the priciest areas to holiday in Europe?? The South is cheaper than Dublin,or tourist areas like Kinsale,but do shop around and look for areas the locals eat and drink for best value.
Have a good trip and I hope your relatives like the place
