Where would be a good one night stop on the way from Dingle to Bushmills? Or should we plan Northern Ireland for another trip? We have 8 nights, 1 night in Dublin, 3 nights in Dingle, 4 nights left to plan but the last will be near the airport. Thanks!
Near which airport?
Dublin airport
Ideally, you would fly into Dublin and out of Shannon, or vice versa. With only 8 nights, you could do do either the north or the south part of the country but you can't do justice to both. As planned, you'll spend way too much time back tracking. Can you fly open jaw?
We did 8 days in Ireland twice, first flying into Shannon and out of Dublin, next trip into Dublin and out of Shannon. Mostly saw the south on the first trip and the north on the second trip, duplicating Galway and Dingle.
With the limited time you have available I'd skip the side trip to Bushmills and save NI for another trip, else you'll wind up spending a great deal of your vacation time in transit.
Better use of your time might be to stay closer to Dingle (Killarney, the Ring of Kerry, maybe the Beara peninsula come to mind) or, if you don't mind a short drive up the coast, head up to Galway with a stop at the Cliffs of Moher along the way. There's lots do see and do around Galway - Connemara is one of the prettiest areas in Ireland, which is saying plenty.
Also, if you're returning to Dublin for your flight home, you could drop your car in Galway and then train from there to Dublin Heuston station, spend a last night in the city, then taxi or Airlink to the airport then next day. Might save a bit of hassle logistically if you didn't especially want to drive it.
Safe travels.