Hi Shona,
Yes, it's a beautiful country but very large. There are too many places to see and never enough time.
CPT and the region is still the best though, and the troubles in other areas don't seem to have reached there to the same extent - yet.

6 bottles should be enough to convince your friends that WA wines can more than hold their own and I'm sure you will have no trouble at all with customs.

4 trips were short biz ones to JNB only but the other 2 were long vacation trips between JNB & CPT by road via lots of interesting areas and another one direct to CPT and Paarl area for several wine tasting days. Can't wait to get back.
Have a good trip.
Peter