Sydney is stunning at that time of year. Grab your accomodation asap as NYE is crazy expensive
Id say a week is fine, there is plenty to do. Beaches are awesome but very crowded. Harbour cruise, bridge climb a day trip to the Blue Mountains...you’ll have choices
XMAS lunch at all the good restaurants will be already booked and expensive wherever you go. Your hotel can help.
NYE is crazy in the city. It’s something to behold and well worth it. But a million people line the shores and it’s hard to find a good spot without knowing where to go. Public transport is the only option, so you’ll u need your hotel to help with suggestions. In an ideal world, I’d be at Mrs Macquarie’s chair - but so will half of the city. Wherever you go, bring food and drink (lots of water as it can be hot) and just enjoy the show. Fireworks at 9 and midnight - the latter being the big one.
Youll love it!