If we go to the trade shows in Hong Kong and Guangzhou as visitors do we need do apply for visa?

Good day,

I and my husband are Planning to visit Hong Kong from 15-27 October 2013.09.13

The reason for my visit is business. I am going to visit
• Asian World Expo Hong Kong
• Mega Show Hong Kong
• Canton Fair Guangzhou
• Jinhan Fair Guangzhou
• Factory in Shen Zhen

I want to order products from the shows and import it to South Africa.
Your assistance will be much appreciated.