How can a family balance Perth, the Pinnacles and the south west in nine days?

Treat the Pinnacles and nearby coast as one focused northern outing. Decide whether to stay overnight by how much time you want there and whether a same-day return would end after dark.

Group the trip into two or three bases rather than a new hotel for every attraction. Perth can cover city time; a separate south-west base gives the family room for caves, coast and food stops.