The 72-year-old musician and his singer wife, 37, recently started a new tour together and are bringing their 9-month-old boy along for the ride.
"We're actually on the road right now," Katharine told E! News. "We're in Florida. David has about 18 tour dates so we are in and out of suitcases from hotel room to hotel room and Rennie's right there alongside us."
She continued, "This kid is headed all over the place, so he's going to be accustomed to being with us. It's great that we're fortunate to have the kind of jobs that we can take him wherever we go. It's great to take a kid to lots of places in their early life."
David put it a bit simpler: "He's a road rat."
Earlier this fall, the couple embarked on another fun musical endeavor, just the two of them: They performed in disguise on The Masked Singer during the past sixth season, and were unmasked on an episode that aired Wednesday, Dec. 8.
When asked if they planned on showing Rennie footage of themselves on the reality singing competition, Katharine told E! News, "Sure, why not? I don't want him to be on YouTube one day and be horrified by what he sees."
As in, "My dad's a banana," joked David.
Katharine said Rennie did not get to see his parents in their costumes and was home with his nanny while they taped the series. She added, "It was a good exercise in work life and mom life, and it went great."
"It was a very weird experience running off to the set every day, because we were having to lie to people all the time," the singer said. "So, for instance, we both have the app called Find [My] Friends so our family, David's daughters, my mom, my sister, my best friends were like messaging me and being like, 'What are you working on right now? It says you're at the studio, the Sunset Gower studio. What are you working on?'"
Their answer? "We told them, 'Oh we're working on a secret Christmas special.' We had to lie. For two weeks, three weeks straight," she recalled.
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