"This is our first time in South Africa and we will do our best [to] enjoy every moment and of course make a difference in people's lives," Venus told reporters at a press conference in Sandton, on Saturday.
Breaking the Mould aims to catalyse, acknowledge and reward South African women who have risen above their own set of challenges and adversities to succeed and inspire.
The duo will host a coaching clinic in Soweto on Saturday afternoon at the Arthur Ashe tennis centre in Soweto and take part in an exhibition match in Johannesburg on Sunday afternoon.
"We hope to show the people of South Africa the importance of doing your best and reaching your full potential," Venus said.
President of Tennis South Africa Bongani Zondi said the sister's visit would go a long way in developing the sport in the country.
"This is going to inspire our little ones – especially little girls. We hope it's the start of a long relationship," Zondi said.
"It has been long overdue, [this is] a visit that should have happened sooner. This is going to help us develop a champion from a previously disadvantaged area."
Serena, fresh from a gold medal at the Olympics and wins at Wimbledon and the US Open, says nurturing success in tennis as well as other environments begins with family support.
"Success on the tennis court begins at home. Families must help nurture the children's skills," Serena said.
Serena also played down her world number three ranking, saying results on grand slams were more important than global rankings.
"I don't worry about my ranking; it's about Grand Slam victories. I'll be number one again – it's a matter of time," she said.
Serena added that in spite of Sunday's match being a charity event, the pair will give their all.
"We're going to go all out in our match. We've never played in SA so we'll do our best. Our fans deserve that," she said.
The Williams sisters' exhibition match takes place at the Standard Bank arena in Johannesburg at 2pm on Sunday afternoon.