The beach should be great right about this time, especially on the Cape side waters. Chapman's Peak is worth the drive (toll of R45 I think it was). The Waterfront has some nice shopping and restaurants to fit any budget. The wine region is a bit of a distance, I think 90min from the city centre so you'll need a car to see that.

Oh, and don't forget Table Mountain if the weather cooperates. Bring a light jacket, it can get pretty windy up there although I was there during spring so things may be different in the summer time.