@alis I've never met a museum I didn't like so I'm probably not very discerning in my museum recs.
But I went to the Chinese Museum last year and didn't give myself nearly enough time to take everything in https://www.chinesemuseum.com.au/
Museums Victoria: https://museumsvictoria.com.au/
Even if you're not a huge fan of tennis, you might enjoy getting a general admission ticket to the Australian Open. You won't be able to go in the main courts but I think it's fun to watch matches on the outside courts, and also just hang out with all the people watching the headline matches on the giant screens. https://ausopen.com/