My friends birthday

In November it is one of my friend's birthday and he was thinking of having a slide jam or racing. we were wondering if we would need any permission or ways to make it safer. He cant spend much money ( he had a birthday party last year, his parents only pay for one every 2 years.)  He was thinking to have it either at some place in lane cove or Norman ave, thornleigh. it was just and idea so he might change his mind but some advice would be helpful

thanks

https://maps.google.com.au/maps?saddr=66+Norman+Avenue,+Thornleigh,...

idea for course at Norman Ave (just idea)

he will be turning 14 if it makes a difference