A royal celebration! Duchess Kate Middleton is “having a modest birthday” to celebrate turning 40 years old on Sunday, January 9, a source exclusively tells Closer Weekly. “She’ll be spending with the people she loves most — her family.”

Prince William, who shares children Prince George, Princess Charlotte and Prince Louis with Kate, 39, “was organizing a birthday party at a private location and invited extended family and old friends from college and university,” says the insider.

“Unfortunately, it was canceled because of the surging number of COVID-19 cases,” the source adds. “William thinks it’s better to be safe than sorry and postponed it to a later date.”

Even so, that father of three, 39, “is still going out of his way to make Kate’s 40th birthday a memorable occasion,” assures the insider. “He has arranged a romantic out of town getaway in January, for just the two of them.”

In addition to William’s getaway plans, the U.K. native “is surprising Kate with a real piece of jewelry; a diamond love ring,” the source dishes.

As for George, 8, Charlotte, 6, and Louis, 3, the little royals “are baking their mum a big 4-0 multicolored sponge and marshmallow cake with 40 candles to blow out and they’ve handcrafted gifts,” the source details. “Charlotte spent hours making her mum a beaded necklace. It’s so cute!”

According to the insider, Kate doesn’t care “about the cost,” she’ll love all her gifts “equally.”

George, Charlotte and Louis Are All Grown Up in Kate Middleton and Prince William’s Christmas Card!
Courtesy of Duke and Duchess of Cambridge/Twitter

The Duchess’ birthday comes two weeks after the family had a magical Christmastime. “George and Charlotte have been begging William to take them to Lapland to meet Father Christmas and all the elves and reindeers, and George is dying to see the Northern Lights, too,” a separate source revealed to Closer Weekly ahead of the holidays.

“William hasn’t made any promises yet, but maybe next year, once travel restrictions have fully lifted,” the insider noted. “So, he and Kate are creating their own winter wonderland at Anmer Hall.”

Of course, part of the festivities included lots of gifts! “Charlotte has asked for a pretty watch and new camera, George wants an outdoor adventure kit — which comes with a tent, torch, cooking kit and walkie talkies — and Louis has asked for a fireman’s outfit,” the source gushed.