My wife joined me after my hunt in Namibia last year. We did a three week, self-drive tour and managed to see many of the sights mentioned above, but it took us all of that three weeks. If you only have 3 or 4 days, you need to make some decisions. Sossusvlei, in the south, is probably one of the most iconic places in Namibia with the red sand dunes and scenery, and they have hot air balloon rides at dawn. It is a long way from Windhoek, on some rough road, but is worth the drive.
Etosha game preserve in the north, is stunning, and you will see many, if not all of the animals on your list. If you go to the front desk of any of the places you stay there, ask them what animals have been spotted and in what places, then off you go. We were lucky enough to see two rhinos squaring off at the watering hole in Halali. This too will take all of your allotted time.
Another idea is to go into and around Swakopmund. While we were there, we ate and drank like royalty! Two places I recommend are The Jetty 1905, located on a pier out over the ocean. Splurge on the Seafood Platter, pair it with some outstanding wines, and roll yourself out of there having only spent what you would have on a luke warm Coors Light and a soggy hamburger at an Applebee's back home. The other place would be the Brewer and Butcher. They make all of their own beer in house (Germans man, they know beer) and serve meat. Lots of game meat on their menu, and I had a Tomahawk steak that makes me cry still to this day just thinking about it. Prices were phenomenal, and your American greenback will stretch for miles.
In the daytime, we did a desert tour with Tommy's Living Desert Tours. This guy makes the desert come alive, and was one of the highlights in the area for us.
Lots to do and see in Namibia, you only need to decide what will be a good fit for your group and the time you have.
Good Luck, and enjoy the planning!