Why not fly straight into Cape Town? Then you can spend as much of your vacation enjoying the delights of the Cape without any regrets of time wasted in travel time.
Look into this option is you just would like to focus on the coast, as such a trip would easily take two weeks, just focusing on the coastline between Cape Town and Port Elizabeth which is known as The Garden Route.
I have flown directly into Cape Town with Emirates. I have flown to Cape Town with a short stopover in Johannesburg, so that some of the passengers could disembark from a Turkish Airlines flight.
You can too!