Are you having the two weeks holiday non stop ? You could really do a lot in two weeks and see a lot of the country but that depends on how much you like driving.

You have about 1400km between Cape Town and Joburg. Can I suggest KwaZulu Natal Umofolozi/Mkuze reserves and then the Drakensberg one week and the other week Cape town. The reserves are linked with each other and have the big five with plenty of rhino. You will also be not so far from the coast to catch some good fishing for big ones as well.