Unfortunately, there are no official free camping areas anywhere near Airlie Beach.
Wind the clock back 15 years and you could just about pull up your campervan anywhere, since then the local council has cracked down and taken that away from us. Car parks that used to be full of people camping are now paid car parks that have strict no-camping rules.
The only place to camp in Airlie Beach is in a paid caravan park or hostel that allows camping. If you are looking for something right in town then Xbase will be your best bet.
If you want to be really crafty about it, you could jump on Coushsurfing and ask people if you can camp in their yard.