As usual, your starting point has to be Thinkspace at the Powerhouse. They’re running a wide range of activities. The workshops generally hit the 7-12 year old range, although there’s one for slightly older kids.
For teenagers AIE usually runs some more serious courses.
GirlCode is running workshop for girls in Bondi and on the Central Coast.
TechScience has courses in Manly on coding, robotics, electronics, 3D-printing and even more.
The Sydney Programming School has learn-to-code workshops running at the Mosman Art Gallery.
Still on the North Shore, Professor Plums is running science and robotics workshops during the holidays. Doomsday Science looks good.
The Australian Museum always has some good-looking holiday activities, including Scientist for a Day and a range of activities exploring Aboriginal culture.
RoboCamps is running at Macquarie University and selling out very quickly.
As always, if I’ve missed anything feel free to let me know.