Everyone likes to plan lots of activities for a family trip, but start your next one with relaxing activities to give everyone a chance to adjust to that new time zone, environment, or just recover from the journey. Then, once everyone's settled, work up to the big events. Image from larrison.
You and your family are probably eager to jump into the awesome trip you've planned, but you'll be tired from travelling. Head to less popular sights where the lines will be shorter, or pick places where everyone can go at their own place (museums, audio tours) and there are plenty of spots to rest. Work in down time where you return to your hotel so everyone can nap or have quiet time to recover. This way, no one burns themselves out on the first or second day of the trip, and you'll have plenty of energy for bigger sights and longer trips later in your holiday.
How to Keep the Peace on a Family Vacation [Wendy Perrin]