The Obamas met five of the hospital's young patients, who were dressed as elves.
"Hey, you guys, you going to help us?" Mrs. Obama asked.
"Good job, elves," the president said. "Nice job."
Jackman, who hosted the concert, also urged the audience to remember those less fortunate.
"It is the season of compassion. Let us not forget those who are down and out, who are suffering and who have little hope: the Washington Redskins fans," Jackman said. "I can say it, I'm a Giants fan."
The Redskins lost to the Atlanta Falcons earlier Sunday and fell to 3-11 for the season. The New York Giants also lost, though, getting shut out by the Seattle Seahawks as their record fell to 5-9.
Other performers at the concert included the Backstreet Boys, Anna Kendrick and Pat Monahan, the singer from the band Train. Retired NBA star Charles Barkley also was on hand to talk about programs at Children's National.
The concert will be broadcast Friday evening on TNT.
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