Can we get away for days trips and return in the late afternoon? Where would you suggest? Three nights in Dubrovnik. In Cinque Terra we did that when the place was overflowing with people. We took boats rides away from the crowds.
Montenegro - Bay of Kotor is beautifully scenic, driving is easy. Kotor itself is kind of touristy if you drive that far. Perast makes a nice stop.
Trebinje, BiH - very untouristy. Interesting town even if not particularly charming.
Drive up the Peljesac Peninsula (Croatia). You could make a very long day of it and take the short ferry at Orebić over to Korcula Town. But that would be a long day trip.
Agree on Kotor- it's easy and worthwhile. Be aware that Kotor also gets cruise ships, so if you can manage to go there on a day with no (or at least not multiple giant) ships in port, it would be delightful and perfect.
Also the Peljesac Peninsula with the little ferry to Korcula would be nice and I think you could do that in a day.
1) Take a day trip on the boat to Cavtat - we were there last summer. Not crowded, nice restaurants, pleasant trip there and back.
2) Find a local from the TI who can take you to back-country restaurants.
3) Walk from the old town to the new town, and see how the locals live. My wife and I did this walk - maybe 2 hours, pleasant, away from the tourists.
The bay of Kotor and a few of the towns along the way are beautiful. But the town of Kotor wouldnt be top on my list after seeing Dubrovnik. Just a smaller version of the same and nearly as crowded as Dubrovnik. But just about an hour further down the coast is Budva. Great spot on the water for an overnight stay. Fewer tourists, beautiful town, substantially cheaper than Dubrovnik, Total drive with out stops; about 2.5 hours. Part of the trip can be on different routes so you dont have to completely back track. Great mountain roads, villages, coast line... https://www.google.com/search?q=budva&safe=off&source=lnms&tbm=isch&sa=X&ved=0ahUKEwia2vXzz7ndAhXBna0KHervC-UQ_AUICygC&biw=1710&bih=964&dpr=1.6