On the way back there are a lot of nice spots around Central Queensland. Deepwater National Park (Which encapsulates Wreck Rock, Middle Rock and Flat Rock), Workman's Beach campsite virtually 1km south of Agnes Water, Tannum Sands (caravan park at the beach), 1770 caravan park on the water etc etc. Inskip Point near Rainbow Beach is also worth a night or two if it's a relaxing trip you're after. Depending on how keen you are to explore near 1770 you can also get into Middle Creek in Eurimula National Park via a 4WD track from the road into Agnes Water.
Cape Palmerston and Five Rocks are another couple of places to look at near Mackay.