Hi, I'm Lynne and will be the Tour Manager on this tour. There are restrictions on how much currency you can take into SA, however as someone mentioned, there are plenty of banks and ATMs available and I will advise you when we'll be near banks etc. Optional activities in SA do need to be paid in SA Rand only. US Dollars can be exchanged at banks or exchanges.
If you are doing the Zambia extension, the currency situation has changed (again!) quite recently and they have gone back to accepting US dollars, sterling, euros etc as well as the Zambian Kwacha. You will, however, still need to have some US dollars for the Zambian visa which you pay for on arrival. I am also able to take a credit card payment for the Zambian optional excursions too.
I hope this helps and I look forward to meeting you at Heathrow in a few weeks time.
Kind regards
Lynne