Mr Bush announced via Twitter that he intends to make a tandem parachute jump near his summer home in Maine. It was a vow he made five years ago when he marked his 85th birthday by skydiving.
Spokesman Jim McGrath said the 41st president likes both a surprise and an adrenaline rush. He said the president hopes to show that seniors can remain active, even though he now uses a wheelchair.
A guest list for a private dinner in his honour includes more than 200 relatives and friends, a family spokesman said.
Many of the guests are from his days in the White House. His children, including former president George W Bush and former Florida governor Jeb Bush, will also be there.
During his presidential years, Mr Bush was known for jogging, tennis and fast-paced golf but now uses a wheelchair.
"He's lost his mobility, but he hasn't lost his heart. He's still the genuine person that we've come to cherish," said Ken Raynor, a friend at the Cape Arundel Golf Club.
The 41st president lives in Houston but has spent every summer at the three-storey home in Maine except when he was a naval aviator during the Second World War.
During the war, he bailed out of his airplane over the Pacific. Later, he decided to jump from a plane of his own accord and marked his 75th, 80th and 85th birthdays by skydiving.
"It's a wonderful day in Maine - in fact, nice enough for a parachute jump," the former president announced on Twitter.
Mr Bush intends to jump from a helicopter with a retired member of the army's parachute team, Mr McGrath said.
The announcement was kept secret until the last minute, partly to give Mr Bush himself the option of changing his mind.
Mr McGrath said: "It's vintage George Bush. It's that passion for life. It's wanting to set a goal, wanting to achieve it. I'm sure part of it is sending a message to others that even in your retirement years you can still find challenges."