Generators as the name suggests produce / generate power they do not however store it.
To me it would seem that you would want to get your self a good deep cycle (or prefferably a couple for redundancy reasons) I would probably look to a couple of gel or absorbed glass matt based batteries at around the 50+ AH (C20) rating and an inverter. You can charge these batteries in a few different ways.
You could look to solar, in which case i would talk to a 12V specialist Derrick from http://www.sidewinder.com.au
has a fair range to choose from and is very helpful. Or else theres a few australian based solar sites with sections designated to solar for camping.
You can charge your batteries by starting your vehicle and connecting them to the charging circuit via an anderson plug and a dual battery isolator. This would probably be best done by an auto elec unless you fully understand a charging system. It will take about an hour of your car running before the batteries are charged to about 85% though...
Probably the easiest way is to get a pair of deep cycle batteries and get a small 4 stroke generator and use the 12V output to charge the batteries or use the generator with a battery charger (will take longer but gives a better charge).
You can pick up small generators fairly cheap these days and the running cost of a generator every day is going to be a lot less than the cost of starting and running your vehicle for an hour at a time.
Also before you purchase a 12V - 240V inverter PLEASE check wether your equiptment will opperate off modified sine wave inverters, These are the cheaper inverters (they are about 40% of what a pure sine wave inverter is worth) they do a good job provided the equipment is suitable unfortunately alot of equipment isnt suitable for modified sine wave use though.
If you need any clairification on any of the above just psost up and i'll get back to you ASAP