With kids, give Day Trip to Kotor, Montenegro a miss.
The drive along the Bay of Kotor is genuinely jaw-dropping and Kotor's own walled old town plus the climb to its fortress make a rewarding contrast to Dubrovnik. The honest catch is the border crossing can mean long, unpredictable queues in summer, it's a full long day mostly on a bus, and Kotor itself now gets its own cruise crowds. Go for the bay scenery as much as the town.