Like Fraser Island, I highly recommend the Whitsundays Islands! What we really wanted to do was go on a tall ship sailing trip through the islands, but by the time we were ready to book they were all full. But what we did was great! We went on a...well basically like a ferry out to Whitehaven Beach on Whitsunday Island. It's the biggest of the islands, but it's uninhabited. The most famous attraction is Whitehaven Beach. Beautiful white sands, gorgeous beach. We were there just at the end of stinger jellyfish season, but the staff still recommended stinger suits. So, we wore lovely stinger suits! :) Basically Lycra bodysuits. :)
After 2 hours there we headed to Daydream Island for lunch and the rest of the afternoon. Daydream Island is one big resort, but it's pretty awesome. Had a great lunch while watching stone-curlews and seagulls fight over food they could steal. The stone-curlews do this odd hissing thing. They look scary, but they're not.
Then we fed some fish in the ocean, took a lovely rainforest walk, mom went into a hot tub for a bit and we just hung out appreciating the beauty. There are two families of kangaroos on the island, one on the south end, on one the north end. Took pictures of them both. :) All in all, a great day.