The Dutch Royal Family never reveal their private plans for holidays, so this is just guessing on my part:
It could well be that Princess Beatrix will spend Christmas and New Years at castle Het Oude Loo in the woods near Paleis Het Loo in Apeldoorn.
She uses that castle often as a weekend retreat and is one of her most favorite places.
It is also near the house of her sister Margriet, who is also going through a difficult Christmas because of the serious illness of her son Bernhard.
I think it is most likely that Princess Mabel and her daughters will spend Christmas with Beatrix, just as Prince Constantijn and his family.
I am not sure about the King and Queen and their daughters. It could be that they are spending the holidays with Princess Beatrix or with the Queens' parents in Argentinia, which they usually do.