The surprise decision was announced at a briefing at Buckingham Palace on Monday morning.
The couple decided once they saw the program that they could take their children, who are likely to be seen on arrival and departure of both countries. The five-day tour lasts from July 17 to 21.
“They have decided that their children, Prince George and Princess Charlotte, will travel with them and we expect the children to be seen in at least a couple of occasions over the course of the week,” their spokesman said.
“They look forward to a busy and impactful tour and are grateful that they will have the opportunity to meet the Polish and German people — such important friends of the United Kingdom — as a family.”
As the couple conduct their official duties, the children will stay with nanny Maria Turrion Borrallo at the Belvedere Palace in Warsaw — where the family will be based from their arrival on July 17 — and at the residence of the British ambassador in Berlin when the family is in Germany.
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Among the highlights of the tour is a fun river race for the competitive couple. They set to take part in a rowing race on the Necker River, Heidleberg, which will include competitors from Cambridge and the German city. The two university cities are twinned.
The race will be a re-match of their famous dragon boat race on a lake in Prince Edward Island, Canada, in 2011.
In Germany, the couple is also set to visit Stutthoff Nazi concentration camp in Poland, the first camp set outside German borders. It was one of the last camps liberated in May 1945.
In Gdansk, Poland, on July 18, William and Kate will meet the founders of the Solidarity movement that campaigned against the Soviet-backed government in the 1980s.
The spokesman added, “As with previous tours, Their Royal Highnesses have asked that this tour allow them opportunities to meet a wide variety of people in both countries.”
“In addition to meeting leaders in business, government and civil society, the Duke and Duchess will prioritize opportunities to meet the young people of both countries; from entrepreneurs, to mental health campaigners, and bright young talents in music and the arts.”
With the tour landing in term time for most British schools — and George set to start full time schooling in September — it is the last time they have the opportunity take them both away while schools are open. “It’s fair to say that school will make this more complicated in the future,” the spokesman said, without wanting to speculate on future tours. “But they are delighted that the program worked out this time for them to take George and Charlotte.”