best overnight stop when driving from Galway to Dingle?

If you are staying overnight near the Burren when you are sightseeing in that area then you could certainly drive from there to Dingle without an overnight. Sounds like you may be going back north to Galway so if that is the case, what about staying in Bunratty near Shannon? Dunaree B&B is just down the road from Bunratty Castle and Folk Park. At Bunratty they offer Medieval Dinners which your son might enjoy. In Dingle there are many wonderful B&B's where you can stay. I think recently there was another posting on this site with several recommendations for B&B's in Dingle. Our favorite is The Greenmont.

Barbara

thanks, Barbara, we'll make reservations.
Also thinking of dropping rental car in Kerry (after Dingle) to fly back to Dublin for 2-3 day of sightseeing in Dublin.
I think Zach would enjoy that more than another itinerary, but not sure.
Is that better than driving south to Cork & Waterford, then driving back to Dublin?
I guess what I'm asking is, would 2-3 days in Dublin be a better way to end our vbacation than 2-3 days in Cork and Waterford for my son and I?

Yes, I think going to Dublin would be better. Dublin offers something for everyone! When we were there last July there were lots of young people on study trips from other EU countries in Dublin enjoying the music and street entertainment, McDonald's and Starbucks on Grafton Street, and hopefully enjoying the historic sites their teachers were taking them to see in Dublin. If you son is interested in history or archeology a visit to the Museum of Archeology on Kildare Street is a suggestion. A fun place to visit is the National Leprechaun Musuem. The young tour guide tells humorous Irish tales. As you know there are day trips from Dublin to many historical sites north and south of Dublin.
Barbara

Looks like your plan is coming together. Have a great trip.