Why not do it the easy way and stay at the lighthouse accomodation, I am sure it will only cost you your first born? At least you won't have to carry much, and the scenery would be awesome.
It is a reasonably easy walk in and out that will only take a lazy half day each way, especially with a light pack.
You could book accommodation at the lighthouse. Park the car at Port Albert, and con someone with a decent sized boat.
Get Gilligan and Skipper to drop you off then pick you up and return to your car.
Or,
spend some pocket money
and get flown in by Helicopter from Tooradin.
Or a charter flight from Mangalore, won't need the 4wd because of Park Rules.
All great ideas!!