Hi Laura,
My wife and I just recently finished a trip up the QLD coast. I think you are definity on the right track with a caravan. Especially if you are travelling for a prolonged period of time. It just gives you that bit extra freedom and space. My mum seems to keep upgrading her caravan to a bigger one and says that bigger is always better. I can testify that a camper trailer or swag will be just way to much of a hassle for you. I can only imagine the difficulty of trying to get some assisstance from an excited 6yr old haha. At least with a caravan you can set it up and then still take Emily into town, etc and be able to know the caravan is locked and secure.

I think you will be able to bargain with the people selling the whole setup if they have given up on travelling. You may even be able to use your current Navara as a bartering chip?

Good luck with the hunt! I look forward to seeing which way you choose to go.