Although children of all ages are able to attend these skate parks, it is more suited to children from about ten years as injuries can be sustained (Isaac's best friend broke his leg last week). This is quite rare because none of the other kids have ever broken anything, so don't let this discourage you.
Adult supervision is a good idea. Bring your own helmet, drinks, snacks and away you go. Penny boards, skateboards, scooters and bikes are all suitable for the Skate Parks.
Click here for all the Skate Parks in Victoria. I find it a pity that there are not kiosks at the Skate Parks. The only Skate Park that I know of that is indoors and has a snack bar and store (selling all kinds of skate accessories) is the Skate Park in Sunshine.