In Sydney? Order an Adventure Passport for your kids. This is a great idea, and a fantastic family service. RIOT had Adventure Passports last year and we got so much use out of them.
“The Passport is an incentive based scheme which encourages you to visit and discover many of our amazing cultural venues. You’ll see and do remarkable things while learning about our world. Walk among the dinosaurs at the Australian Museum, sample school life in 1888 at Rouse Hill House & Farm, take the sculpture garden challenge at Campbelltown Arts Centre or learn about shipwrecks and rescues at Newcastle’s Maritime Centre. The Passport is for NSW K-6 primary school aged children only and provides free entry for Passport holders to participating venues.”
Basically, your kids get free entry into the listed venues, and have their passports stamped upon entry. Be quick, this offer ends in April.