I agree that the little villeages on the Blackall range ridge would be a nice option as you will be seeing enough beach in PD. The views from up there are gorgeous.
Another fun place is the town of Eumundi which has great markets on Sat. and Wed. mornings. I have stayed at the Kingfisher Lodge, and it is beautiful- a true ecologically conscious resort and from there you can get tours of Fraser Island.

Enjoy your trip!

Val