I started not to write a review since the itinerary is changing. However, I do have some suggestions to pass on for anyone going on a cruise with tour information.
We did a pre-cruise for 10 days. We booked with Kensington Tours. I can't say enough good things about them. They took care of everything from air, hotels, and tours customizing them when asked. We weren't in to all day snorkling/diving at the Great Barrier Reef so they found a boat ride that included a glass bottom boat and a little snorkling if we wanted. They were quick to respond when we contacted them with various questions.
My estimate is that we saved around $900 per couple over what Princess wanted for their 5 day pre-cruise.. While we didn't get to go to Darwin, our pre-cruise was much more inclusive We built in a day in Port Douglas to rest after a grueling 24 hour in-transit from Houston. Not so with Princess, you immediately board a plane to Ayers Rock and go on a tour when you get there. Princess tour was "slam, bam, thank you ma'am " while we had some rest time built in with ours. We had additional tours included, too. If you go to Ayers Rock, the very first thing you do is get a "head net." They cost about $7.50 apiece. The flies will carry you off during the day getting in your mouth, ears, nose, eyes, etc.