Thought I would give the boat a little plug http://www.houseboatescape.com.au/ because it was very luxurious and the owners are such nice people!
Jules piloted the boat himself with no problems, and we were up and down the river for a week; we had to have the Paringa Bridge raised for us (which stopped traffic and impressed the kids) and went through a lock twice. All VERY entertaining.
We chugged past the SA/Vic border too..... saw heaps of wildlife including a big goanna which I didn't get a picture of.....
The boat was very safe for the kids, although you still have to have some common sense and watch them - so if you're thinking about a really different holiday, one so totally relaxing that you come home looking 5 years younger - this is IT!