I've done the Garden Route / Outside Cape Town twice with the non kiting wife and 9 yr old. So in CT my main focus was kiting also up at Llangabhan. Not so much outside of Cape Town, down the garden route it was more of an added bonus as we were doing family stuff. That said I kited Witsand, Still Bai, Plett, Sedgefield and Oyster Bay. If you're in an RV then I would just follow the wind and research camping spots you can get to.
Have a look at this link.
Just back from Cape Town for my 4th trip, last two, solo trips for a kite break. For the uninitiated the wind can be light 15 knots 12m weather and the fiercest wind you can imagine. 40 knots plus, sand blasting your legs to bits. Cape Town is full on when the wind is in, if you're not used to big waves and strong wind then getting a flotation vest.
ohh and you pay the locals for parking, between 3-5 rand. I would not recommend not paying. I find tipping a few rand here and there goes a long way. Don't leave anything in the car that can be seen.