A good question.
A local answer.

Choose a hotel by the route back after a late session, not only the morning walk.

Keep licence and booking requirements handy, and inspect the vehicle before leaving.

Choose one main food market and one different-style market if the weekend is short.

Keep a rest day between coast and mountain sections and confirm suitable child seats.

Keep city sights together before collecting a car, then give Phillip Island and the Great Ocean Road separate travel blocks.

Check the current timetable and disruptions before leaving so the return does not become an unplanned late trip.

Choose shopping areas by the styles and budgets the group enjoys, then check current opening days for smaller shops.

For snow, check current conditions and the child-seat and clothing arrangements before paying for a private transfer.

Choose the vehicle everyone can use comfortably on long driving days, with safe child restraints and enough luggage space.

Set a firm time to start the return to the port so the last beach stop does not threaten boarding.

Check the forecast again before departure rather than packing for a single average temperature.

Choose the farthest essential stop before fixing the overnight; Apollo Bay is a base, not a promise that every landmark fits.