somewhere to go away camping (yes im still kind of new to it :))

Hi ..
Being new to this i have a question that i would like to ask. taking my kids (8 and 13) camping a few wks ago down to a camping ground at Rathdowney, i found that they just loved it an would love to go again. Not realising that it was goin to be school holidays and great weather that everyone is deciding on going away camping im now sittin here trying to decide what im goin to do. i cant not take them an disapoint them since they have been lookin forward to it but i got no idea where to go i would like to go somewhere that isnt goin to have a million ppl there, im happier to camp were there isnt many ppl .. long as there are some kind of toliet around the kids will be happy. i dont really want to travel too far something within say about 5hrs drive of brisbane. where they can at least swim, maybe go for a bush walk. they would like to head towards the nsw and qld border but i dont know where to take them. ive been to girraween which i think they might enjoy for a couple of days but i dont know about the croud since we wont be leaving untill either the 31st september or 1st october. ive also been down to sundowner. i also have to take into consideration that we dont have our own 4x4 an may have to borrow a friends station wagon since lol my car isnt big enough for us when we go camping.
any help and suggestions would be greatly appriciated.
thank you in advance
brisa