If u are from Reunion, maybe u know Herkul? Or even Louis Rouillard? Can hook u up with them.
Anyways, your trip is quite challenging. Because with big van, u can do only 80-90 km/h, and the distances are huge. Particularly coz u can drive only in daylight, it is not advised to drive at night on open roads.
U might easily hit a kangaroo, cow, or even a camel up North in the sunsets or night. And this is scary s.it..
When it blows, it blows hard particularly above Geraldton. And that might be too much for you guys. It is a no go, the waves will be nothing like u used to. U need to plan for injuries, urgent help it very very far in remote areas.
The best bet is to stay in Safety Bay for u guys. Half of your trip there, and around Perth, than go South. The kids will love it, Penguin Island is there, flat water, kite school, etc. Gear fixing, bla bla
Also, it is very very expensive. The petrol up North is much more expensive. Food too, water, everything. As mentioned, flies there are absolute nuisance, your wife and kids might struggle with that.
The nature for me is way more beautiful down South. But thats me. Margaret River, Busselton, Yallingup, Pemberton, Augusta, Denmark, Albany, Walpol, all stunning if u take local roads and not freeway. Eating out, winaries, huge caves, walking tracks, stunning for kids too. North is too dry for me, I love trees, hillsides..
Sharks? On open Ocean? They are everywhere, don’t worry.