Hi - all the information you need can be found on Word Travels' sister site Expat Arrivals - see our detailed South Africa expat guide here:

http://www.expatarrivals.com/south-africa/moving-to-south-africa

In answer to your question, the salary seems decent enough, but what about the benefits: wil the company pay medical aid, provide a housing allowance, security, etc? These are your biggest expenses in South Africa. Schools can be excellent, but they are expensive. Read the guide above and good luck to you.