Port Germein is about 240km north of Adelaide. The fishing is quite good up there, so I hope he's got a boat! It may be a bit of a shock for you. The temperature would have been about 38C (around 100deg F) over the last couple of days.
There is some beautiful country up there. A little further north are the Flinders Ranges. We go camping up there when ever we can, but it's now starting to get quite warm, and you can't have a camp fire in most places. ( It doesn't seem to be the whole camping experience without fire to sit around at night) I'm sure you're uncle will be able to show you plenty of sights.