On Friday President Jacob Zuma announced the mourning period for Mandela, the founding father of modern South Africa and its first black leader, after he died late Thursday aged 95, surrounded by friends and family.
Obama, America's first black president, will travel to South Africa next week, the White House said, joining a raft of world leaders for a huge December 10 memorial service.
Mandela's body will lie in state in Pretoria for three days before he receives a state burial on December 15 in his boyhood home of Qunu.
The logistics are daunting for hosting the great and the good who plan to fly in from around world to honour the universally respected statesman.
The official SAPA news agency quoted a travel industry official saying that "very little accommodation will be available in Johannesburg and Pretoria" in coming weeks as the South African government and various consulates block book hotel rooms.
Memorial events begin Saturday with thousands expected at a wreath-laying event in a Johannesburg park.
Obama and his wife Michelle will travel to South Africa together with former first couple George W. and Laura Bush.
Ex-president Bill Clinton, who was in office when Mandela took power to become South Africa's first black president, also said that he would be making the trip with his family.
White House press secretary Jay Carney said the Obamas would "participate in memorial events" without giving details.
In a tribute shortly after the revered statesman's death was made public, Obama mourned Mandela as a "profoundly good" man who "took history in his hands and bent the arc of the moral universe towards justice".
Australian Prime Minister Tony Abbott said he would attend the memorial to honour "a truly great world leader, an extraordinary man".
Brazilian President Dilma Rousseff will also be among those flying in next week, her office said.
On Friday, ordinary South Africans across the country poured out onto the streets in a riot of colour, dance and song to celebrate the life of their beloved ex-leader, known affectionately as Madiba.
In Cape Town, a crowd of thousands from all races and ages gathered for a multi-faith celebration at the site where Mandela made his first public speech after nearly three decades in apartheid jail.
"Tonight we stand in solidarity as the people of Cape Town -- black, white, coloured, Indian, all the religions together," said mayor Patricia De Lille.
South Africa's archbishop emeritus Desmond Tutu, a fellow Nobel prize winner, praised Mandela as an "incredible gift that God gave us".
Fighting back tears, Tutu said his old friend was "a unifier from the moment he walked out of prison".
Mandela spent 27 years in an apartheid prison before becoming president and unifying his country with a message of reconciliation after the end of white minority rule. He shared the Nobel Peace Prize with South Africa's last white president, F.W. de Klerk, in 1993.