A good question.
A local answer.

Group nearby stops on the same day; returning across the river repeatedly can take more time than the map suggests.

If you wait, allow time for ticket setup and security queues rather than arriving at kickoff.

Check the actual table view, child-friendly choices and booking time; a restaurant's river address does not guarantee every seat faces the water.

Compare a debit card with your credit card's own foreign transaction fee, which is separate from any local merchant surcharge.

In warmer weather, start early, plan shade and water breaks, and avoid trying to cover every exhibit.

A river ferry can be part of the visit, but use the current timetable and allow a land transfer to the terminal rather than relying on a ferry alone.

If the tickets are separate, allow a much larger buffer or take an earlier domestic flight.

Bring footwear for wet paths and have a dry-weather alternative; never enter water where signs or conditions say it is unsafe.

Use the same card or device consistently for taps where supported, and verify any child or concession fare requirements separately.

On departure day, allow for peak-hour road traffic or public-transport transfers and the airline's check-in deadline.

If that cost is too high, arrange luggage storage and plan a gentle breakfast until the room is ready.

If the port call is short, a closer wildlife option may give you more time with animals and less time on the road.