"And he was desperately keen to come, the problem was any US president has so much pressure on their schedule and bluntly, we're a well behaved citizen."
Key said US presidents typically get dragged off to difficult places or vastly big places and we were neither.
It was not clear where the golf would be played or where Obama would stay.
Now the official title was gone and the pressure was off, he had been keen to head Downunder.
Speaking as the former Minister of Tourism, Key noted the trip could provide a boost to our economy.
"The reality is, you get a bit of worldwide exposure as he posts things," he said.
"Just encouraging people to come down, getting a bit of exposure to New Zealand, that's all got to be pretty good."
Although Obama was no longer president, he would likely continue to have a big influence in the United States.
Key said Obama initially wanted to come for longer with Michelle and their daughters, but his schedule only allowed for a few days.
Talking golf, Key said he had been playing "okay" - but he wasn't counting his birdies before they flew.
"Butch Harman, who's probably the most famous golf coach in the world, once said that there was 10,000 people that could break par on a PGA course in America on any given day," he said.
"But only 100 of them could do it while the lights are on and the cameras are rolling.
"I might be in that category - talking big and it's horror city tomorrow when we get out there."
However the game played out, Key assured Hosking the game would be played fair and square.
"Unlike a lot of politicians who are known for using the foot wedge and ignoring the rules, he is a stickler for the rules," he said.
"He's the true lawyer, he knows all the rules and he follows them."
Obama would receive a Maori welcome at Government House in Auckland on Thursday and is expected to meet Prime Minister Jacinda Ardern there.
Obama has been brought to New Zealand by the NZ-US Council to promote the relationship between the two countries, which was icy for many years over New Zealand's anti-nuclear policy.
He will speak at an invitation-only dinner for 1000 people on Thursday night in Auckland.
His trip is part of a four-day swing around Japan, Singapore, New Zealand and Australia.