I can only second that suggestion - I don't know where you're from or your religious or cultural perspective, but climbing on Uluru always strikes me as the same as walking in to St. Patrick's Cathedral in New York or Westminster Abbey in London and climbing on the altar.

This is very ambitious and I would not recommend it. To drive to the Twelve Apostles and back to Melbourne by 5pm is just about impossible. The Great Ocean Road is a windy, single lane road with a lot of traffic. Most people would plan on at least two days if they were planning on going as far as the Twelve Apostles. Though the Great Ocean Road would be good, you'd be far better to simply spend the day in Melbourne. You don't want to do "a quick drive tour of the city." Melbourne, particularly the central area, is much better explored on foot. The central area (bounded by Spencer Street on the west, Spring Street on the east, Flinders Street on the south and La Trobe on the north) is criss-crossed with alleys and laneways - which are full of shops, restaurants, cafes and bars. Much of Melbourne is "hidden" - down an alleyway, up a stairway, behind an unmarked door. Exploring Melbourne on foot would easily occupy your day and give you a taste for one of the world's great cities.

In Sydney, I'm not sure about the dinner cruise. I'd go on the harbour during the day - take the ferry to Manly (from Circular Quay), walk up the Corso to the beach, have coffee/breakfast/lunch and get the ferry back. A pleasant trip and a great way to see the harbour and the sights from the water. The Blue and Red Explorer buses will take you all around the land-based sights to see in Sydney and are an excellent way to get a quick(ish) overview of Sydney. The Bridge Climb is well worth it, if you have the time and the money.

What ever you do, enjoy ....