Homebush Aquatic Centre. It doesn't always occur to people to go swimming on a rainy day, but when the water is heated and there are hot chips from the cafe to be consumed and washed down with a good coffee whilst the kids run amok, why not!
Monkey mania in the Entertainment Quarter is always fun. Adults pay entry which includes a free coffee. Lots to see and do there for kids, and there is no time limit. Its a great way to celebrate kids parties especially through the winter months. They have themed party rooms, a cafe and lots of obstacle courses to choose from. They have a few locations in Sydney but this is my first choice since its at the entertainment quarter, you can spend the whole day there also with
lots of restaurants, sunday markets, movies and shopping to explore.
Those kids play parks are fantastic. Many shopping centres have great play equipment like at Macquarie. A kids flick at the movies is always good fun. Indoor kids play parks such as Wannabee's in Frenchs Forest is also good.
Being a big kid myself, I've always been one for a great indoor adventure. The best thing I love to take my neice and nephew to is Bowling in Macquaire Centre. Besides having amazingly fun bowling, the laser tag and games room are great for keeping any child engaged. Make sure you've got a few gold coins in your wallet though because the kids are going to want to play the claw game... and inevitably lose.