The CSIRO has a nice range of science activities coming up. One of the good things about the CSIRO programs is that they’re spread all over the place rather than just being in central Sydney.
The Australian Museum has a range of activities, mostly aimed at 8-12 year olds and focused around the dinosaur exhibition. Activities include Scientist for a Day looking at “Did dinosaurs really die out all those years ago, or do some remain today? Could the study of genetics allow us to recreate our own Jurassic Park?” Another course has students making dinosaur cookies.
At the Sydney Observatory holidaying students can investigate Saturn and look in entirely the opposite direction by becoming an archaeologist. The Observatory activities seems to be generally aimed at a slightly younger crowd starting with 5-year-olds.
Sydney Olympic Park has Fizzics Education doing some engineering with workshops on Lego robotics, making catapults and building with Mecano. Fizzics is also doing a workshop in North Sydney on forensic science.
There’s also the usual wonderful range of coding and electronics workshops from the perennial brilliant Thinkspace at the Powerhouse Museum.