In around Spinnaker sound marina you can usually find poddy mullet over the beachside around the boat ramp .
You can also find bream around the boats from the shore .
It is on the mainland side just before you cross the bridge , can't miss it .
As for other beach spots , never really fished the main beach , but i hear the whiting fishing is good on the SW end of the island .( i don't do a lot of land based )
There is a bit of a drop off there and i have taken some niceflatties aswell.
Plenty of boat hire options if you want to get out and run around the passage .
and you can pick up 4 crab dillies for around $25 and try your hand at a few sandies aswell around the banks . don't have to travel far , whiting and flatties can be pulled off the same banks
I would take you for a run but i am out of town . See Mark down at the Bribie boat hire and Kiosk ( on the beach next to the boat ramp at spinnaker ) Tell him Tim told you to have a yarn with him , he can let you know whats biting and where ...he also has boat hire and bait in shop !
Best of luck to you !