Wedderburn on the southern side of Sydney is worth a drive, there is a big variation of Aircraft from homebuilds through. Usually a friendly bunch there, you can have a look around without the need for an ASIC which is a security pass.
Albury is another spot on the way to Melbourne, if you can have a look at Murry Griffiths show there, he rebuilds/builds warbirds.
A good drive from Sydney is to follow the coast all the way round to Melbourne, you could call in to Wollongong where they have quite a bit of stuff from DC3's to a Constellation. There are a lot of very nice places down the coast, a few smaller airfields to what you'd be used to interesting anyway.
If you decide to travel inland a must see is the Temora aviation museum
http://www.aviationmuseum.com.au/
Try to time your visit with a flying weekend, it's a great show with stuff you won't see anywhere else in the world.
At Melbourne there is a good museum with all sort of machinery including a Beaufighter.
Distances between towns will be a bit of a surprise for you, there is a fair bit of driving between Sydney and Adelaide.
Once you work out a rough programe let us know and we can give some more advice on where to see stuff.
SP