As you can see on the map, the first big town on the ‘inland route’ between Adelaid and Sydney is Mildura. I’ts about 5 hours drive from Adelaide so that would make a nice first stop after a travelling day. It is located next to a river (the Murray), so there are bound to be some activities with boats. And it’s pretty close to the Perry Sandhils, appearantly a known background for lots of movies:
The Perry Sandhills are 10 hectares of striking red sandhills that were once part of the huge Willandra Lakes System and date back to an ice age 40,000 years ago. Evidence suggests that the Barkindji people lived here since ancient times and bones of mega fauna found in the sandhills also reveal that huge kangaroos, wombats and other creatures once roamed the region. Located 5 kilometres from Wentworth near Mildura.