Synney is gorgeous in spring/summer, not so sure about this season. Don’t miss the ferry over to Manly and visit the Corso but that maybe that is at it’s best in summer. I love their national parks but they are a bit out of town. Also the Queen Victoria Buildings are just beautiful. It’s worth taking an organised tour around The Rocks - so much history and a tour guide really helps. If you or your cousin suffer a brain injury during your visit, my son is a neurosurgeon working locally. Just in case you need him.