Have a family trip planned this summer. Last time we were in Ireland we were in the Republic of Ireland so figured we'd check out Northern Ireland this year. We were planning on a car rental for most of the trip like last time, however it's looking like the flight home will be from Dublin.

Still trying to figure out the best way for transportation otherwise. Would prefer to return the car to Belfast if possible. Any suggestions on the best transportation to get from Belfast to Dublin? Can do car rental if necessary but would think it's going to be very expensive crossing the border plus one way rental.