Their Dec. 23 nuptials in snowy Park City, Utah, might have been “incredible and beautiful” – according to T.R. Knight – but Katherine Heigl and Josh Kelley’s Mexican honeymoon got off to a rocky start, a source tells PEOPLE.

First, the Grey’s Anatomy star forgot her passport, so “the happy couple could not fly directly to Cabo,” says the source. Instead, the two had to stop over in California first.

But things brightened considerably when the couple made it to Mexico. Kelley, 27, enjoyed some tee time, the source reports, while Heigl, 29, soaked up the sun.

And by Friday, the happy twosome was spotted poolside as Kelley serenaded her new bride – and friends – with songs from his upcoming album.

People