Oh man that is awesome Trav
welcome to ten Tenths btw.
mabs in Australia the usual age is around 7 or 8 for starting out , in England they are called cadets , here in Oz we call them Midgets.
I spent several years racing myself and used to love heading out onto the track when these young guys and gals come on and doing some flagging , they had an absolute ball.
but yes check with a local club , I believe you are in Western Australia so check this site
http://www.kartingwa.com.au , it may help you I just did a quick goggle and found it but didnt read through it.
also has a list of WA clubs so choose the one closest to you and you will get the answers you need from them Im sure of it.