Hong Kong can be fantastic for children if the itinerary has enough breathing room. The goal is not to tick every attraction but to mix different kinds of experiences.
Morning
Choose one major attraction while everyone has energy.
Lunch
Pick somewhere quick and flexible, especially if children are hungry.
Afternoon
Use an indoor attraction, ferry ride or easy neighbourhood walk.
Break
Build in hotel or café time rather than waiting until everyone is exhausted.
Evening
Choose a simple dinner and an easy waterfront or neighbourhood stroll.