A good question.
A local answer.

Choose a flexible airport ticket if flight arrival time is uncertain, and keep your payment method ready for the city trip.

Check airport pickup directions and any late-night service gap before choosing on price alone.

Compare hotel locations against the specific South Bank venues you plan to visit and the nearest bridge or station.

Check that your phone supports eSIM and is unlocked, then compare coverage maps for the places you will actually visit.

If you will make frequent rail trips, a property closer to your chosen station may save more effort than a cheaper uphill room.

Compare the app's waiting and cancellation terms with requesting a car after you have collected your bags.

Choose one walkable river or parkland area for each free block rather than spending the short trip crossing town.

If ocean surf is essential, accept the longer public-transport trip and choose one beach with a straightforward return.

Confirm late check-in and the rental desk's morning hours so the overnight stop actually simplifies the trip.

North Stradbroke has settled areas and road access, while parts of Moreton need organised transport or suitable vehicles.

Reserve a ride that reaches check-in with a buffer and confirm the vehicle can carry your group's bags.

Allow for terminal transfers, weather disruption and baggage storage; a short island stay may leave little margin.