"I think Gwen enjoys learning a little bit more about us," Luke Bryan jokes to PEOPLE

Gwen Stefani may have shocked a few country fans when she took the stage during boyfriend Blake Shelton‘s set over the weekend, but Luke Bryan says the pop star was right at home at his Crash My Playa music fiesta.

“I think Gwen enjoys learning a little bit more about us country people!” Bryan jokes to PEOPLE. “But she totally fits in and has a blast.”

Shelton brought Stefani to the four-day music event in Riviera Maya, Mexico, and the couple soaked up the sun and surf as much as the stage. “They’re excited to be on vacation and we’re happy they have the ability to enjoy themselves,” says Bryan.

Blake Shelton Gwen Stefani
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Credit: Kevin Earle

Bryan hosted Crash My Playa — a chance for even the stars to do some “total vacationing and chilling out” between sets, he says — for the third year, welcoming Little Big Town and Brothers Osborne along with Shelton. But the singer is celebrating a much bigger milestone this month: a decade since the release of his first single, “All My Friends Say.”

“My wife Caroline and I sat in bed the other night talking and jokingly said it’s almost like we’ve lived a lifetime in 10 years,” Bryan says. “We’ve had some wonderful moments and we’ve had some trying moments for our family but we try to take it all in stride.”

Bryan says he can look back on those early days, and early tunes, with fondness — and a sense of humor.

“You could call me cheesy, but I was doing the best I could at the time,” he says. “I’d wake up every day and do the best I could. And my approach now is no different than that 30-year-old guy in Athens, Georgia, at that video shoot. Back then, I was 30 trying to look 23, and now I’m 40 trying to look 33!”