Adelaide is the centre of Australia’s wine industry, and there are lots of wineries, restaurants, and other farm & foodie things to do.
The Barossa valley, McLaren Vale, Adelaide Hills, Victor Harbour and other places are all nearby for day trips.
In the city itself there are loads of restaurants, cafes, various museums & art galleries all within an easy walk.
You can catch a tram from the city to the beachside suburb of Glenelg: the sand is fine and the sea is calm, albeit a little chilly.
There’s quite a bit of info on the South Australia Tourism website.
There’s also a guide to events and festivals on in Adelaide