"Our Christmas story," she wrote on Twitter. "Time to find our Christmas tree."
Photos showed the singer with "Big David" (fiance David Otunga) and "Munch" (David Jr.), 3, at a Christmas tree farm. Big David carried a saw and little David tried to help.
"Munch thought he saw Santa in the sky!" wrote Hudson, with a photo of the boy sweetly looking up.
Meanwhile, it was announced Thursday that Hudson will join Forest Whitaker and Angela Bassett in new musical movie Black Nativity.
Adapted from a Langston Hughes 1961 text, Movie Web says it's the story of a teenage boy from Baltimore who is sent by his single mother to Harlem to spend Christmas with the grandparents he's never met. Hudson will also appear in a guest role in the second season of NBC's Smash.