Charles, 66, and Prince George, who turned 2 last week, have enjoyed playtime on the grounds of Charles' grand country home, a royal source confirms to PEOPLE.
The proud grandpa recently treated his grandson to a garden picnic, complete with plastic cups, the source says.
He was also able to show George the sweet garden hut he was given to mark the little royal's first birthday last year.
The Victorian-style Shepherd's Hut, which comes complete with a day bench bed and a little stove in its cream-painted interior, sits on a wrought-iron frame with cast-iron wheels, resembling an old gypsy caravan. It was given to Charles by the craftsman's company, Plankbridge, which got its start through Charles' Prince's Trust charity.
The hut sits close to a wildflower meadow near a shady, secluded play area called the Stumpery, which features a refurbished treehouse that's perfect for a prince.
The treehouse was originally built for Prince William in 1988. And if little George is anything like his father, he'll love escaping to it.
As a young boy, William told the treehouse designer, Willie Bertram, that he wanted "it to be as high as possible, so I can get away from everyone. And I want a rope ladder, which I can pull up so no one can get at me," according to landscape artist and writer Bunny Guinness.
George is "still a little young" for the newly thatched treehouse and hasn't played in it just yet, a royal source says. But George and his little sister, Princess Charlotte, will have many fun playdates to look forward to in the treehouse, which is known as Hollyrood House (after the Queen's home in Edinburgh, Scotland – and because it was built in an old holly tree).
"Charles and Camilla absolutely adore being grandparents and are enthralled with Charlotte and George. Charles is a warm and caring guy, but he comes even more alive around little George. He loves spending time with him," a source close to the royal family tells PEOPLE.
See Prince George Show Off His Toothy Smile in Adorable New Birthday Portrait
Each year, Prince Charles opens the Highgrove gardens to visitors – raising about $1 million for his charities in the process from the tour and gift shop.
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