I have launched a 12ft tinny at cygnet bay pearl farm and left the car in the parking lot for a few days to explore some of the buccaneer archipelago. You may have to pay a fee to leave the car at the parking lot which is fair however when I left the car there they did not charge me anything (I’d already been camping there for a few days though). You are best off launching above half tide as the beach is shallow, sand is hard though if you do need to drive the boat out a bit to launch it. I’d suggest calling ahead to ensure they are happy to accommodate you and to ensure no conflict with their operations. I’d also recommend crossing the king sound inlet (east of sunday island) at the change of tide due to currents and standing waves.