If you're in the Saint Kilda area these school holidays, take the kids to the Adventure Playground, where they'll have the time of their lives. As soon as they see it they'll run off and want to do everything at once.
The playground has a huge pirate ship type play equipment which they can run around on. There's a slide, tunnels, sandpit and trampoline to keep them on their toes the whole day. I went here with my cousins once and they loved it. They really enjoyed the very large rocking horse as well.
For the older kids there's a tree house, and what kid doesn't want to hang out in a tree house?
The best part about the playground is that there's lots of sun shade, which is what I don't usually see at parks. Its good in case it's a super sunny day and the kids want to keep cool and protected from the sun.
There's also an awesome metal drop type slide (its very small). I went on it with my four year old cousin and he giggled the whole time. He made me go down it at least 20 times, it was pretty fun though.
The kids will go crazy here, its definitely a playground like no other. Take them at least once while they're young so they can experience it. I guarantee they'll be begging you to take them back.
The park opens are 3:30 pm - 5pm from Monday till Friday and 11am - 5pm on Saturday and Sunday. The only problem is that sometimes it is closed. You can arrange to have your kids birthdays here too, but you'll need to call up and ask.
There's two hour free parking in surrounding streets. I'ts only a short walk from Luna Park.