The Royal Babysitters by Clementine Beauvais (author) and Becka Moor (illustrator) (UK edition)

Anna and Holly have spotted an advert in the paper for a Holy Moly Holiday – the intergalactic vacation of a lifetime. They simply CAN’T not go. But how will they get enough money? Simple: they’ll become royal babysitters for a day. Unfortunately, the girls are in for a shock. Once King Steve and Queen Sheila have left, they discover there isn’t just one prince to look after. There are six. And worse, the country’s arch enemy, King Alaspooryorick of Daneland, has decided to stage an invasion. Will the girls be able to keep their royal charges safe and still go on their dream holiday?