Mugabe, a guerilla leader who swept to power after Zimbabwe's independence from Britain and went on to rule for 37 years, died on Friday, aged 95.
His health took a hit after he was ousted by the military in November 2017, ending his increasingly tyrannical rule. He had been travelling to Singapore for treatment since April.
"I can't give an authoritative day, all I know is people are leaving tomorrow Monday to go and pick up the body," Leo Mugabe told AFP.
"So assuming they get there on Tuesday and the body is ready, logically you would think they should land here on Wednesday," he said, adding that a list of accompanying family members was being finalised.
Once praised as a liberator who rid Zimbabwe of white minority rule, Mugabe soon turned to repression and fear to govern.
He is widely remembered for crushing political dissent and ruining the economy, prompting mixed reactions to his passing.
At Sacred Heart Cathedral, Mugabe's parish in the capital Harare, the priest encouraged congregants to pray for their founding leader.
"I know some of us may have different feelings about it, but it’s our duty to pray for one another," Father Justin Jagaja told AFP.
President Emmerson Mnangagwa declared a period of "national mourning" on Friday, without providing further detail.
The government is expected to announce when Mugabe's body will be returned to Zimbabwe and provide details of the funeral in coming days.
Mugabe's family and Mnangagwa appear to disagree on whether the former president will be buried in his rural homestead Zvimba in a ceremony involving local chiefs, or at the National Heroes Acre -- a hilltop shrine in Harare commemorating guerillas killed during the liberation struggle.
Leo Mugabe refused to comment on the feud. "All I know is (that) we are closer to an agreement if the chiefs meet up with the president and discuss the issues," said the nephew.
He explained that his uncle would have been appointed chief of Zvimba had he not become president.
Zimbabwe's deputy information minister Energy Mutody said the body would rest in Harare.
"His Excellency President ED Mnangagwa has declared former President Robert Gabriel Mugabe a National Hero," Mutody tweeted on Saturday.
"The former President will be buried at the national heroes acre at a date to be announced."
The 57-acre site, presided over by three bronze guerilla soldiers, was later opened up to national heroes in the arts and academia.
The family of Zimbabwean Afro-jazz icon and human rights activist Oliver Mtukudzi also refused to bury him at the shrine.
Mtukudzi, who succumbed to diabetes in January, was declared national hero for his social and political influence.