However you do it from the West Coast, you are looking at at least one stop and two long legs. From SAN, you can do one stop on BA via LHR - good but not sensational product, but would allow you to fly into CPT and out of JNB or vice versa, and may include a CPT-JNB segment in the price. Or one stop via JFK on whatever plus SAA - two separate tickets, which is far from ideal and you will pick up an extra stop on the return for SAA to refuel. SAA is acceptable but not great.

From LAX, you have many more one stop options. Cathay, Qatar and Swiss probably have the best products in J. Also consider Air France and Lufthansa. The best easy way to look for fares is to use kayak.com.

Finally, one way fares will be staggeringly expensive. I would suggest that, if you want to use miles but don't have enough for two of you, use miles for one and buy a return ticket for the other.