Hey there! Local Perthie here. Here's some answers:

1. There will be maxicabs there. There is literally no other un-stressful way to get to Fremantle unless you know people who can pick you up.


2. Early August it will still be a little cold. This winter has dragged on a long time. Be prepared for below 10 C at night and maybe close to 3-4 C due to the winds in Fremantle. Bring a jacket. Day time will be nicer with the sun coming out. Just be warned it can get cold


3. Not sure about this one sorry!


4. Depending on what you want to do, you can do either. Hilary's has a great steak house - Hippo Creek as well as AQWA for the kids to play at. Rottnest has, well, more summer things. I'd go for Hilary's, if the weather was not that of summer or spring, which it probably won't be.



Extras:

Not sure why you are taking the hop-on hop-off buses. In the city there is free transit through the three different CAT buses. They go to nearly all the sites including Kings Park.

Swan Valley is great, good food and wine. Chocolate factory is fun for the kids.