Welcome!   

We would be glad to help make your trip memorable, but we would need a little more info, please.

Dublin to Galway is about 4 hours by car, driving direct, but you mention Northern Ireland -- Is the plan to make the trip VIA the North?  Galway is considered West or North-West.  The North would be Counties Down, Antrim, Derry, Fermanagh and Tyrone.

LOTS to see and do along either route, but you would need more than one night traveling through the North if you actually wanted to visit any of the sites.  Mostly along the "Direct" route are places like Clonmacnoise or Strokestown.  Birr and Potumna/Mountshannon areas are also rich in beauty and historical sites.

Please clarify.