More than 90 expressed interest in the trip, but more than 40 applications were subsequently withdrawn when medical checks revealed some veterans could not make the long journey.
The trip has been fully funded by Veterans' Affairs New Zealand.
"There will be some disappointment among those who are not able to attend," Mr Ottaway said.
About 6000 New Zealanders flew in bombing raids over Europe during the war, braving anti-aircraft fire and fighter aircraft to attack German targets.
One of them was Bruce Cunningham, now aged 92 and living in Wellington, who became a prisoner of war after parachuting clear of his Lancaster aircraft when it was hit over Belgium in 1945.
He said he will never forget what went through his mind as he watched his mates fly away while he parachuted to ground.
"I distinctly remember thinking: 'They're a mile above me, I'm sitting down here ... and they're going home for eggs and bacon'."
He was caught, and spent time in a Russian detention camp from where he twice tried to escape.
Bomber Command crews had the highest Allied casualty rate of World War II, with 55,593 men killed, including 1851 Kiwis.
Another veteran, Frank Prebble, said it is important to remember the men who did not come home.
"When you stand at that memorial and think of all those guys that have gone, I think that will be an important moment," Mr Prebble said.
Britain's Daily Mail reported that construction of the memorial faced opposition from local authorities and a lack of support from the Ministry of Defence and the National Lottery, but was helped along by the backing of a couple of big-name pop stars.
The Bee Gees' late Robin Gibb and Jim Dooley of the Dooleys threw their support behind the project.
"It has been so moving, the support we've had," said Mr Dooley.
The roof of the memorial is made entirely from the aluminium of a wrecked Halifax bomber dredged from a Belgian swamp.
Mr Dooley said the Canadian government melted down the Halifax bomber and then delivered the aluminium roof.
Every London cabbie has promised free passage to any Bomber Command veteran tonight.
The memorial also pays tribute to those who lost their lives due to the bombing with the inscription 'THIS MEMORIAL ALSO COMMEMORATES THOSE OF ALL NATIONS WHO LOST THEIR LIVES IN THE BOMBING OF 1939-1945.'
The New Zealand veterans not able to attend the unveiling ceremony in London will take part in a commemorative ceremony in Wellington later this year.
