3 days in Sydney with 3 small children - what should we do?

[Kellamity]

We are staying centrally, will be a bit tired after the mammoth journey but need to see the child friendly highlights!

Children are 8, 6 & 2

Go to the aquarium to see the duck billed platypus
Go to the zoo to see koalas and wombats

Go to the botanical gardens to see strange plants and run around, plus it used to be free, and may still be.

Go on the ferry to Manly.

Go to Bondi beach and play.