With kids, it depends on the day.
The greenest, most restorative day-trip from Dubrovnik — pine-shaded saltwater lakes, a boat out to St Mary's islet, and cycling paths that feel a world away from the crowds. The honest catch is the ferry logistics eat a chunk of the day and the park entry plus transport add up; it rewards nature-lovers far more than monument-hunters. Best done at a relaxed pace.