A good question.
A local answer.

Most venues accept cards, but keep a backup payment method. Book meals that matter to you and check any dress requirements at the individual restaurant.

Check the current itinerary, lunch arrangements and cancellation policy before booking. A private tour can be tailored but still cannot shorten the distance.

Pack layers that you can remove during the day: a light warm jacket, comfortable walking clothes and something for rain or wind.

For a park walk, check current track and weather notices, carry water and set a return time before dark.

Choose an indoor activity that matches your interests, such as a gallery, performance, covered market or long lunch, rather than forcing a museum visit.

It can work if you choose a small number of stops and start early. Check the door-to-door drive from your Sydney base.

Choose Darling Harbour if the dining and entertainment around that precinct appeal more. Check the route to the rail or light rail stop from the specific hotel.

Front-row seats can feel immersive but may require looking upward or miss part of a wide stage. Decide whether closeness matters more than an overall view.

Look at the exact hotel entrance: Darling Harbour covers a broad area, and some routes include hills or crossings. Check walking times for your group.

A day trip can work if you pick one village and a small number of sights. Check train times and the last return connection before leaving Sydney.

Check the ferry timetable in both directions and have a bus alternative in mind if the service pattern does not fit your lunch. A short neighbourhood loop is enough for a half-day.

Carry water, sun protection and layers. Set a turnaround time based on the slowest walker, especially on routes with steps or exposed sections.