Fiji, New Caledonia, or Great Barrier Reef Island
 

Hello. My husband and I are having a tough time deciding on which of these places to visit for the last week of August and first week of September.
We have been to New Caledonia before and love it there. We have also been to the Great Barrier Reef on a live aboard scuba dive boat, spent time in Cairns, and up in Cape Tribulation. We have vacationed in Australia many times and have always enjoyed it immensely.
We feel comfortable and safe in returning to either of these destinations, but, it seems, part of the excitement of travel is in seeing new places. We've already made several trips to French Polynesia and the Cook Islands, and been to Vanuatu, so it seems like it's time to visit Fiji. (The original plan was to swim with humpbacks in Vava'u, Tonga, but this plan collapsed.)
After pouring over guide books and dozens of websites, we've narrowed our focus to the Yasawa and Kadavu island groups, but would these places be too windy at this time of year? Has anyone experienced these areas at this time of year? We are looking for an island with a white sand beach with calm clear waters and excellent coral reefs right off the beach.
The other possibility we are considering is visiting an island off Northern Queensland. Is Magnetic Island a good choice for snorkeling right off the beach? Will it be windy? Will the water be too cool? Are there better islands (we can't afford Lizard, Heron, Hayman, or Orpheus--as we would like to keep our daily room cost under $200). Again, I have scoured my guidebooks and numerous websites (including Trip Advisor) and haven't found any answers to my questions. As the folks on this travel board are well-traveled and have helped me much in planning previous trips, I thought it would be a good idea to post my questions here.
Thank you.