I’ll be in Australia for

I’ll be in Australia for a few weeks this August and I need to figure out what to do for a few days. We (Kay and I) have at least eight days to kill between the time we land in Sydney and the time we have to be in the Claire Valley (near Adelaide). Flights don’t seem that expensive, so we’re open to hopping around AUS as needed.

We’re thinking a few days in a nice hotel in Sydney is sufficient, then heading to Melbourne to check things out. After that we’re thinking of doing a train trip from Melbourne to Adelaide, but that leaves a lot of space in between. I know a few people in Australia, and there are probably more that read this site, but what would you do with some free time in Australia? Is there a city I’m missing? What’s the weather like in August? If there’s one thing I have to do in Sydney, what would that be? Should I check out Perth? The northern coast? Hop over to NZ? Try boxing a kangaroo?

Thanks in advance.