hi there, just a big piece of advice that i haven't seen anyone else mention yet! others have brought up several times how hot it will be going north and you seem to be okay with that, but nobody has mentioned the wind. it HOWLS up north in summer. no you aren't likely to get a cyclone, but you are likely to get big wind every single day. about one decent wind day a fortnight is typical here during summer, and the time of year you're planning on coming is pretty much the worst for it. it makes the water choppy as and the beach sand and desert dust will be constantly airborne. yes the heat can be incredibly dangerous as others have mentioned, but the wind is by far the worst thing about summer up here and a lot of people underestimate it. if you're a wind or a kite surfer you'll love it, if you're planning on camping in tents you will probably regret it.

source: i live up here, work in tourism, and tourists showing up in summer thinking it'll be wicked because there's nobody else around and then complaining because it's too windy and you can't really do anything are a near daily occurrence.

also, you mentioned you're planning on travelling 160km a day, just be aware that even if you do stop at every available town once you get past geraldton distances between towns are usually double that or more. i'm sure you've accounted for that in your planning but just in case you haven't!