I understand that most of South Africa’s caravan population sleeps 11 months of the year in Gauteng. Hence the concentration of business there for your enterprise.
Nevertheless a good case exists for having at least a seasonal presence at the coast, particularly in the resort cities, since the need for your product and service will be most keenly remembered. I imagine that even the simple act of distributing business cards and leaflets will have a positive outcome for you.
The experience of my neighbour at Richards Bay, where his holiday was seriously diminished by back injury, is I’m sure not unique amongst the older set of caravan users.