Have an In car DVD installed to the headrests for entertainment on those longer legs of a trip.
In Car Fridge between the kids to keep the drinks cool and food fresh. Also gives them easy access to drinks if they need it and can get you one without having to look for it.
In Vehicle Food Warner / Pie Oven like a Travel Buddy for heating up food while travelling keeps the costs down.
Take Regular Breaks to keep you and the Kids refreshed.
Do some research on the areas you are travelling so you can talk about them with the kids while travelling.
When setting up camp, make sure everyone has a job to do. Even the kids can help with getting the pegs and poles ready or setting up chairs.
Get some High Visibility Vests for the kids. Makes it easier to see them and find them in a crowd.
Call in at NPWS Offices and similar. Many of them will have kids activity books with activities related to the areas where you are travelling.
Slip, Slop, Slap, Wrap before you head out. It is easier to get the kids covered and you know you have everything at the beginning of the trip.
Fit a reversing camera to the vehicle. Can help when attaching camper trailer / caravan as you can see the coupling as well as the safety of seeing what is behind you that is not as tall as the lowest point of the rear window.
I have been into camping and travelling for around 40 years, between family trips as a child, Cubs, Scouts, Venturers, Fishing Clubs and 4WD Clubs.