Our family (2 children + mum & dad), stayed at this beautiful house in this lovely part of Sydney for a week in January. We loved every minute of our stay. The view towards the harbour is simply breathtaking. Lots of toys and things for the kids to play with. Great kitchen, loads of gizmo's, a brand new BBQ and so much space. The pool has a big glass wall down one side so you can see people swimming under water - definitely a highlight for the children.
Holly was an wonderful host and always contactable. She was very helpful for any questions we had about staying at this amazing home or the local area. Mosman is central and the location of the house is very quiet with no passing traffic. You can walk to the river to get a ferry to Circular Quay and even walk to Taronga Zoo which is definitely worth a visit (if you can get your family to leave the house!). There are beautiful coves and beaches 5 mins drive e.g. Balmoral Bay. Ubers arrive in minutes and there is parking easily available on the street outside.
I cannot imagine that you could find a nicer home, or host, for your family holiday to Sydney.