"Look, I know there are some bad ones in here, but this is the last time I'm doing this, so we're not leaving any room for leftovers," said the president of the United States, commander-in-chief and most powerful man in the world.

Yawn! said Austin Robinson, six-year-old nephew of Barack Obama, standing at the president's side in a blue and grey sweater.

Possibly aware of the kindly-leave-the-stage gesture, Obama looked down at the boy and asked: "How am I doing? Good? Thumbs up?" Austin smiled.

Change had come to the White House. Since 2009 Obama has performed the traditional pardoning of the national Thanksgiving turkey while his daughters have humoured him and his terrible puns, with expressions betraying amusement, bemusement and boredom.

But on Wednesday the door of the Oval Office swung open and there was no sign of Malia or Sasha. Instead Obama was accompanied into the rose garden by Austin and four-year-old Aaron, sons of his wife Michelle's brother Craig Robinson, on a sunny but crisp November afternoon. They were admirable deputies, even when it came to irreverently timed yawns.

As for Uncle Barack, far from being downcast about the prospect of handing over the White House keys to a man he warned would flush his legacy down the toilet, the mood was jovial, liberated, even a little demob happy. And for White House staff, plunged into tearful despair by the election result, it was nine minutes of daft escapism.

Obama admitted that he has previously embarrassed his daughters with "a corny-copia of dad jokes about turkeys". He added: "This year they had a scheduling conflict. Actually, they just couldn't take my jokes any more. They were fed up."

Austin grinned.

Fortunately, Obama continued, he had by his side the two nephews, who, unlike Malia and Sasha, "have not yet been turned cynical by Washington. They still believe in bad puns. They still appreciate the grandeur of this occasion. They still have hope."

The president added mischievously that he had not yet told his daughters "we are going to do this every year from now on. No cameras. Just us. Every year. No way I'm cutting this habit cold turkey."

With that he raised a hand and grinned at his watching staff, who groaned, then turned to Austin: "That was pretty funny." The boy kept smiling.

When Obama said he wanted to leave it all out on the field in the final year of his presidency, few realised he meant every last gag imaginable. "I want to take a moment to recognise the brave turkeys who weren't so lucky, who didn't get to ride the gravy train to freedom, who met their fate with courage and sacrifice and proved that they weren't chicken."

A baby in the audience yelped. Obama: "Oh, it's not that bad now, come on." He laughed.

A year ago at the same event, Obama had poked fun at the Republicans vying to succeed him, "a bunch of turkeys trying to win their way into the White House". This time he resisted the temptation to joke at President-elect Donald Trump's expense.

Instead, after a deeply polarising election, he made a plea for unity: "We have to see ourselves in each other because we've all got families we love and we all have hopes for their better future and we lose sight of that sometimes and Thanksgiving's a good time for us to remember that. We have a lot more in common than divides us."

Austin peered at the president's lectern, perhaps wondering how much more of this there was. The answer was not much.

Obama went on to pardon Tot and its backup Tater ("the vice-turkey"), both 18-week old, 40-pound turkeys raised in Iowa. Schoolchildren from the state had submitted pairs of names for this year's turkeys.

Austin and Aaron got to touch Tater's white feathers. "Kind of soft, huh?" said Obama. The bird stood and flapped its wing enthusiastically. "Right on cue!" the president laughed.

The turkeys had stayed at the prestigious Willard Intercontinental Hotel near the White House on Tuesday night. The White House had asked Twitter users to vote for which turkey should receive the pardon, though both did. It provided a biography for each bird: Tater's favorite snack is worms, and Tot prefers tomato slices.

They will be on display for visitors at their permanent home at Virginia Tech's newly built "Gobblers Rest" exhibit where they will be cared for by students and vets.

George HW Bush was the first president to formally pardon a Thanksgiving turkey, though tales of spared turkeys go back to Abraham Lincoln's presidency. In 2014 a Republican official accused Malia and Sasha of looking bored and said they lacked class; the official later apologised.

For all its frivolity, the ceremony is just one example of soft power: there are countless such public events where the US president is required to display class, elan, grace and wit, greeting celebrities and citizens with an easy manner. It will be a test for Trump. For his part, Obama conjured one more deathless phrase: "Yes, we cran."