I can only agree with Dave and Kurt. I think you've been given sound
advice there.

The drive between Jhb and CT CAN be interesting if you want it to be.
You don't have to trake the direct route.

You could go up the west coast to Lambert's bay, then inland to
Calvinia etc. and then approach Johannesburg from the west.
There are intersting places such as Kimberley for example to visit if
you're interested in that sort of thing.

If you're really ecclectic, there's the Radio Museum in Van Ryhnsdorp
:-) and the largest post box in the world in Calvinia. ;-)

Marc