Queensland - 7 days for Outback and Beach Trek?

Hi all,
I'm planning a 4WD trip starting in Brisbane and ending in Brisbane, in that time I have 7 days to hopefully spend a couple of nights camping in the outback and would also a couple of nights campingand sand driving, i.e Fraser or Rainbow beach. Purpose of the trip (apart from to get away from it all) is to take a younger brother on a trip over from England and show him some of what Australia really has to offer.
I'm almost happy to just get in the 4wd and head west for 2/3 days, and then turning north and then north east to do a circular route back to the coast, i.e. up to Hervey Bay for a jump over to Fraser, some time there before straight down the coast to Brisbane. So many options and does anyone know of a sensible itinerary? At the moment it looks like Brisbane towards Gunnamulla but turning off to the Culgoa Floodplain National Park to camp for a night, next day to then head towards Eulo and down to the Currawinya National Park for another overnight camp. After that I guess we need to head north and then back towards the coast, at this point I'd just take it as it came - is this a crazy idea and have we gone far enough west to reach the true outback?
Any help much appreciated, if you've done a similar trip please do let me know, in the meantime I'll keep looking!