When i looked into it, there weren't that many choices and only in one or 2 clusters. We ended up booking bimbi park (camping under the koalas)
That worked for us because we needed 2 separate rooms
But as we were driving, there were many more places then we saw online from America .
If u don't need a specific size room, i would book that day, because you don't know how far thru the GOR you will be and where u want to spend the night