March is close to the end of the season but we still get reasonable wind.
Check out
http://www.nswkba.com.au/locations for locations around Sydney and beyond.
Botany Bay is good for beginners.
Local shop is Kitepower
www.kitepower.com.au/Not sure about camping close by. There is a caravan park on Botany Bay - Grand Pines
www.caravancampingnetwork.com.au/nsw/syd/the_grand_pines.html. It is across the road from the beach.
As a committe member of NSWKBA (AKSA) I encourage membership. Bring a wetsuit. You'll probably only need your 11m kite.