Hey Craig,
Not a cheap option, but Cairns Coconut resort is a top spot. Lots of activitys for the kids (if applicable) otherwise just a really nice, clean leafy invoroment.
We stayed there in 2011 on our way to the cape. Liked it so much we stayed there again on the way home. There is also City Caravan Tourist Park, they are cheap. But we stayed there in 09 and would never go back. There were a lot of perminant reserdants and the place was not very tidy. Left a lasting impression that is for sure.
The place may have changed, as it has been 4 years. Just my 2 cents, based on personal experance. Have a great trip, i would go the the cape every year if i could, it is gods country up their.