1. Taronga Zoo is fantastic and you get in for free with a Melbourne Zoo membership! Catching the ferry over from Circular Quay is the easiest way to get there.
2. Public transport is excellent. Grab an opal card and ride the trains, buses and ferries that are all fully accessible. Circular Quay is a hub where you can get to practically anywhere.
3. The Powerhouse Museum is free with the Melbourne Museum membership and it has lots of interactive fun for kids.
4. Darling Harbour is a lovely place to walk around and there is a pretty amazing playground with huge waterplay area.
5. Barangaroo Park is Sydney's newest public space. It has stellar views of the harbour and is the perfect spot for a picnic lunch. It is an easy walk from the rocks or Bridge.