My husband and I are visiting my daughter in school in Adelaide; in addition to a weekend on Kangaroo Island, what else should we do, including day or overnight trips from the city? Also we propose to drive from Adelaide to Melbourne overnight, taking in the GOR; is this a feasible time table and is it worthwhile from the west to east direction? Many thanks; through "lurking", I've already found many good advice here.

Driving the GOR from west to east is just as good as the other way. You would need to allow at least 2 overight stops on the way though.

you could do it overnight, but there's a bit you can see along the way, so I think it'd be a shame to race though (but you may have constraints). i have done GOR east to west and west to east and I do think it's easier to see the scenery driving east to west, but that said it is fine from west to east as well.

Many thanks; we'll try to squeeze out a second night; any recommendations on where to stay?

How about Mount Gambier for your first night (about 440 km from Adelaide) and Port Campbell for your second night, which would then leave you 250 km to get to Melbourne, allowing time to stop and look.
From Adelaide you could either take the main highway to Keith and then turn south which would take you through the Coonawarra wine area or follow the coast along through the Coorong area (great for bird watchers).
In Mount Gambier, check out the Blue Lake.
Between Mount Gambier and Port Campbell, turn off the highway at Port Fairy and have a wander around the town and port area - one of the nicest old little towns in Victoria. Good fish and chips on the wharf.
Between Port Fairy and Warrnambool, you could stop at Tower Hill - extinct volcano now a national park.
Once you leave Warrnambool, you will be on the Great Ocean Road. Follow that through to Geelong, then the freeway into Melbourne. In Apollo Bay, look out for Mariners Lookout - great views over the coast. Lorne is another good place for a lunch or coffee break.

1* I assume that you are not going to drive overnight (i.e. DURING the night) from Adelaide to Melbourne along the GOR. That would be way too tough a drive. The direct route between the two cities, along the Dukes and Western Highways, is about 730k, and going via the GOR would add about 200k to that. So one overnight stop seems essential, two advisable.
2* The GOR does NOT go all the way from Adelaide to Melbourne: It really starts/finishes at Anglesea near Geelong, and basically ends/starts at about Peterborough to the west. This, with sightseeing, is a fairly busy day's drive.
3* To get to Peterborough from Adelaide, you have two choices: (a) the Princes Highway around the coast, a distance of about 650+k, or (b) via the Dukes and Western Highway to Ararat, then down through Mortlake to Peterborough, a distance of about 700k. In either case, you will have had a good 7 hours of driving before you reach Peterborough, and you may not be up for a great deal of sightseeing when you arrive.
4* At Peterborough, you enter the Port Campbell National Park which features the 12 Apostles, Sentinel Rock, London Bridge, The Arch etc etc, all offshore items of interest. Port Campbell is about 12 k from Peterborough and is probably the place where you should stay overnight. There are hotels and motels there.
5* Next day, the drive on the GOR takes you inland for a spell through the Otway Ranges before you reach the coast again at Apollo Bay. You will want to stop here for a glance around, and from here to Anglesea, the GOR runs right at the edge of the ocean, and is a truly spectacular drive. I last did it two days ago. Lorne will also be a stopping point, but there are many, and you will be disappointed if you rush the trip.
6* From Anglesea, you can drive via Geelong to Melbourne in about 90 minutes.
7* VERY IMPORTANT INFORMATION: From Apollo Bay to Anglesea along the GOR, the maximum speed limit is 80kph. Observe it, because the road is very windy, and the local constables are very savage!

You could stay the night at Port Fairy and drive to Geelong and Melbourne in a day. Stop at Teddy's Lookout in Lorne as it is a good chance to see the coast from high up, and not far from Lorne and a short walk from the car park.

thanks for all the good advice;we revised plans and will do it in two nights,keeping a careful eye on the speedometer!