"I think in a turbulent world, which has been the last decades of the 20th century and now the 21st century, he offers really that sense of dignity, the sense of perseverance in what is good … [and] what is just," Machel said.
Mandela's political activities began in 1943, when he joined the ANC to campaign against the apartheid regime.
As resistance grew stronger, the ANC was outlawed and in 1964, Mandela was charged with treason.
He was sentenced to life in prison for attempting to overthrow the government, and was finally released on February 11th, 1990.
Mandela shared the Nobel Peace Prize in 1993 with FW de Klerk, then South Africa's president, becoming the country's first black head of state the following year.
He stepped down from the presidency in 1999 and has spent most of his time since campaigning for Aids awareness.
Surprise in store
Ndileka Mandela, one of the former president's grand-grandaughters, said "a surprise" was waiting for Mandela in Qunu.
"We do not want to give too much away as it would be like knowing what is in a present before opening it," she said.
"For him it is a special day, but for all of us too."
|Mandela was imprisoned by South Africa's apartheid government for 27 years
The private celebration on Friday comes after public events to mark Mandela's birthday.
An open-air concert in London and the launch of coins and stamps bearing Mandela's image have raised funds for his charitable foundation.
Thabo Mbeki, the current South African president, and Jacob Zuma, leader of the ANC, are expected to be among about 500 guests at Saturday's celebration in Qunu.
A boxing tournament is also scheduled to go ahead to reflect Mandela's keen interest in the sport, while a concert is set to go ahead in Johannesburg's Mandela Square.
De Klerk paid tribute to Mandela, calling him a key figure of the 20th century.
"After his inauguration, Nelson Mandela used his personal charm to promote reconciliation and to mould our widely diverse communities into an emerging multicultural nation," he said.
"This, I believe, will be seen as his greatest legacy."
Zelda le Grange, Mandela's personal assistant, told Al Jazeera that he "personifies what [humans] want to be".
"While he says he has vices and virtues like any other human being, he is what we want to be," she said.
Sepp Blatter, president of football's world governing body FIFA, which awarded South Africa the 2010 World Cup, said Mandela was the "epitome of grace and dignity, a man with determination to overcome even the greatest odds".