Stellensbosch is not far from CPT... and it is a nice drive. Good wineries, too. I visited a few, one I really liked was Hartenberg. And their wine is very reasonably priced. And you are going in March, which is the harvest season (season in so hemissphere are reversed)

Drive south from CPT down the peninsula, is a beautiful drive,too.

I know you have a short time...but the town of Knysna on the garden route is beautiful. Go there if you have a chance... sounds to me like your time is limited,though.

Go to Table Mountain, there is this air tram that takes you there...but walking it is also great, the views are incredible, not a bad hike, maybe 2 hrs up, and then quicker on the way down.