DWTS date night?

New parents Nick and Vanessa Lachey -- who welcomed son Camden September 12 -- sat front row at Monday night's Dancing With the Stars taping, where they cheered on Nick's brother Drew during his dance with partner Anna Trebunskaya.

"Vanessa looked gorgeous," an onlooker tells Us Weekly of the Wipeout host, 31, who wore dark jeans, a black top, a cream blazer and black stilettos. "She was glowing."

Nick and Vanessa sat next to Drew's wife Lea and the couple's daughter, Isabella. "Vanessa talked to Drew's wife a lot," the witness shares.

Before the taping began, an emcee warming up the audience came over to chat with Vanessa and Nick's six-year-old niece.

"He asked her who she was rooting for and she said, 'Drew Lachey.' He asked why, and she said, 'That's my dad!'" the eyewitness says. "The warm-up guy asked what she would have rated him on week one, and she said a 9. He asked what [Drew] would have to do to earn a 10 . . . and she said, 'Work hard!' Vanessa was really cracking up at this and so was Nick."

Throughout the taping, "Vanessa and Nick seemed really cozy and were linking arms," the witness adds. "They had their hands on each others' legs."