J84
Why not track coastal for the northbound part of your trip. Stop at YBMC for a feed.
(It's walkin distance to Mudjimba beach if it's a hot one. Might also be able to bum a lift on one of the transfers buses and get a bite at the Novatel)).
After that head to Noosa then inland over Mapleton & Maleny,Glasshouse mountains and Lake Samsonvale and into YBAF via the TV Towers. You could then head across to Mt Tamborine (lookout-It's YBAF's training area)then back over the Gold Coast hinterland to YBCG.
Like Pierre said, if it's a nice day you'll have plenty to look at on the way north and on the way back.
Enjoy your flight