A good question.
A local answer.

Compare total cost and walking distance to the hotel, not just the fare quoted per passenger.

Check current Western Australian child-restraint rules for the exact vehicle and child's age.

Confirm with the airline whether bags transfer and whether both boarding passes can be issued at origin.

Book a room that accepts very late check-in rather than asking the children to wait in the terminal for hours.

Check the rental depot's next opening and whether luggage can be collected after an evening city stay.

Check the airport's current pickup point and compare cancellation rules in case immigration takes longer.

Check the current terminal transfer time, security and international exit requirements against the airline's minimum connection.

Compare today's rail and bus journey with a direct car using luggage and connection risk, not an old quoted fare.

Tell the hotel about the late check-in and confirm a fallback pickup if the last public service is missed.

Compare current metered guidance with a fixed transfer quote, including card or airport fees.

Allow time for any terminal transfer and luggage, especially if another flight is on a separate ticket.

Confirm the airport's current luggage-storage service and the time needed to recheck or clear security.