I went to most of the places you mention when I visited OZ. In my opinion:

Sydney - is just another city. Nothing special although the promanade from Circular Quey to the Opera House and through the Botanical Gardens to Mrs.Maquaries Chair is a pleasant stroll.

Blue Mountains - Didn't get there :(

Olgas and Ayers Rock Sunset walk - Marvelous. Very worth while.

Aboribignal Dreamtime and Bushtucker tour - The Dreamtime is not to be missed. I found the Bushtucker tour very tourist oriented.

Michelmas Cay Cruise - Didn't do that. Took the Ferry to Manley Island, had a nice walk there and the Ferry back.

Excursion to Kuranda including Tjapukai Cultural Theme Park - Absoulutely wonderful! Very, very impressed by the Kuranda Rain forest and enjoyed the cable car ride, and the scenic train.

Cairns/Great Barrier Reef - You will be diving? Scuba or snorkel it doesn't matter it is beautiful!

Lots of other things to see and do downunder too.

Have fun! Debby - Israel