You often don't need to worry about remembering exactly when your child is due back to school after the holidays; their behavior will tell you. In that final few days, your child will be grumpy, frustrated and upset. They love their breaks from school, when every day is a play day and nobody's trying to teach them math, but what's a holiday for them is often the complete opposite for you.
Without school to provide them with a structure, your child is now mainly looking to you for entertainment. You'll be expected to provide them with an itinerary and something to do on a daily basis. You can go on a family vacation, but that's still likely going to leave you with some time to fill. You'll love having your babies home with you for the first few days of the break. By the end of it, you'll be impatiently counting the hours until you can take them back to the school gates and have a break of your own.