We just came back from a week of yachting and kitesurfing in the Whitsundays. I had a good chance to look around the locations and as far as the Whisunday islands go Whitehaven Beach is the only really safe and open beach for kitesurfing.
And it is also one of the most beautiful places in the world!
We were on a hire yacht. Easy enought to take the gear ashore on the dinghy and launch. Always a good idea to have someone stay with the yacht / dinghy in case things go wrong.
Whitehaven is a long, open beach which is best in SE to NE winds which are the prevailing winds most of the year. Just be mindful of the current as the tide differences are big and the current flows along the beach (north or south) - its very hard work if the tide is following the wind. The conditions are basically flat to choppy water but the reason to kite here is for the colours.
There are plenty of sting rays at the Hill Inlet (north and best end) but they are fairly easy to spot against the white sand.