A few months ago, I emailed Almitywife, asking about (sort of) affordable ways to take a Canadian family diving and snorkelling on the Great Barrier Reef. She suggested Lady Elliot Island and linked us to her photos and their website.
We just got back yesterday, and it was our best vacation ever. We saw the whole range of marine life we were hoping for: Lots of green turtles, bull rays, a couple of mantas, maori wrasse, giant grouper, black tip reef sharks, white tip reef sharks, and lots of smaller fish and invertebrates The dive staff were really friendly and well-organized. The wind was fairly strong (15-25 knots from the E last week), but diving on the W side was fine. Our 8 year old had a fantastic time snorkelling in the lagoon, and our 12 year old loved the reef on the W side of the island. Seeing the turtle hatchlings run to the sea was also a highlight.
Thanks again for this great recommendation!