A source told The Sun newspaper: "This will be the biggest send-off since the death of John Lennon.
"Robin was so very highly regarded in the industry and this will be reflected in the turnout.
"Robin's boys, Spencer and Robin-John, are also working on ideas for their dad's farewell."
Robin died from cancer of the liver and colon on Sunday aged 62.
The star's funeral will be held near Thame, Oxfordshire, where he lived with his wife Dwina.
Robin's cousin Hazel Gibb-Shacklock called for her famous relative to be posthumously knighted by Queen Elizabeth
She said: "We were pushing for Robin to be knighted in the New Year's Honours List because we were very aware that he was ill. If anyone deserves one, it's him. All three of the Bee Gees should be knighted."
Robin's twin brother, Maurice, died in 2003, leaving their elder sibling, Barry, 65, as the only surviving member of the group.