Guys there are awesome kite spots every 10-50kms all the way up the east and west coasts of oz... thousands of them! Just ask around as you travel, learn as you go - there's too many to plan ahead. As long as you stick to the coast you'll never be too far from a decent kite spot.. but make sure you talk to locals as you go, there's nothing like a bit of local knowledge before you go out at a new spot.
In April the season is ending up below about central QLD... the SE'er that we love in summer shifts up the coast around that time and a bit later. By the middle of winter (July) there's trade winds and warm waters up the top end. Lots of the east coast kiters hit Cairns or Port Douglas (far northern QLD) in winter, for 24 degree water and 27 degree air temps, with average 15-20kt winds. Watch out if you go up there, you'll need a stinger suit till April or May at least, depending on the stinger season.. and how much risk you want to take. Some of the locals up there wear one all year round. They look a bit gay tho