The mariachi band serenading Savannah Guthrie and Michael Feldman down the aisle after their "I do's" was not the only surprise in store for guests at the couple's hush-hush weekend wedding.
Just as family and friends – an intimate gathering of 80 to 90 people – were sitting down to dinner, NBC anchor Guthrie, 42, and Feldman, 45, said a few thank-yous and reminded guests to keep the nuptials secret until Guthrie could announce it herself on air on Today Monday morning.
That's when the DJ hit "play" on a recording of the NBC News "Special Report" music, an insider at Saturday's sunset celebration outside Guthrie's hometown of Tucson, Ariz., tells PEOPLE.
"Savannah looked at Mike, and said, 'So, should we break some news? Okay. I – we – are four months pregnant!' It was an explosive moment. Everyone was on their feet, cheering," the source reports.
Among the immediate family and handful of closest friends were Jon and Dorothea Bon Jovi, whom Feldman (a Washington D.C. communications strategist) befriended through his work in the Clinton-Gore White House, and Guthrie's Today co-hosts Matt Lauer, Al Roker, Hoda Kotb and Willie Geist.
It will be the first child for both Guthrie and Feldman, who met in 2008 when she tagged along with a mutual friend to his 40th birthday party. They started dating the following spring.
Just last August, Guthrie told ELLE, "I would love to have kids. I hope so, if we're lucky and blessed, but who knows what life holds, you know? I'm 41 years old."
After flying straight back to New York for work on Monday morning, Guthrie, who plans to keep her last name, will take a honeymoon (call it a combo honey-babymoon?) in April. Lauer tells PEOPLE: "She's a hard-working lady."
For more exclusive photos and all the inside details from the wedding, see the upcoming issue of PEOPLE, on newsstands Friday.