Not sure if it helps much, but I have only done a sunset on the beach with a jetty ...Noarlunga, Brighton and Glenelg. Jetty road in Glenelg may be a nice place, little closer if you are staying in the CBD (nice for dinner too).
We went out the other night for a sunset and it was a real poor show, hope it is better for you.
Have a good time in Adelaide hope you get to see lots.
cheers, Rosemary