We were in Melbourne just 2 weeks ago and had planned to do the Zoo but it was far too hot so we went to the museum and both our girls loved it - so did we. DD1 is nearly 4.5 yrs and DD2 turned 2 in mid Dec.

The Melbourne Zoo is beautiful though and both our girls LOVE going to our zoo (we are members so just pop in regularly) so that would be my pick if the weather is favourable. Take a stroller though, it's big!

We've also been to the Aquarium when DD1 was 2.5 yrs and she loved it. She still talks about it! So that's another great option if it's hot or raining and therefore no good for the Zoo.