A good question.
A local answer.

Group the national museums and galleries by area rather than crossing the city for one stop at a time.

Check current road conditions and book a family room at a stop with an easy arrival.

Compare the experience length and total family price with a standard zoo visit or another guided outing.

Choose fuel and rest stops that can accommodate the full rig rather than relying on small roadside turnouts.

Give each day one major museum or gallery and pair it with a park or short outdoor break.

Check current cafe hours within a short walk, especially for the days you will leave early.

Check current Christmas menus and booking policies directly with hotels and restaurants well ahead of the day.

Compare a greener neighbourhood's daily travel time with a central hotel before paying for extra space.

Check driving time to the family attractions you plan, rather than choosing by city-centre distance alone.

Compare the current rail timetable, station transfers and total door-to-door time with the flight.

Map each hotel to the museums and walks you actually want; Canberra attractions can look close but be spread out.

Look for a different angle on a familiar landmark at a quieter hour instead of driving to many lookouts.