How to arrange meeting times for cruise shore excursions to avoid missing the ship

The biggest fear with cruise shore excursions is vague meeting times. Once guests get off the ship, they see shops, photo spots, and restrooms, and easily assume they still have time. If one person is missing at the actual meeting time, the whole bus has to wait. Cruise itineraries are different from regular land tours; missing the ship isn't as simple as just catching the next bus. When I…