Give the grandparents (or sitters) some leeway with bedtime, food, and any nonsafety issues. Make sure they feel free to show an extra episode of his favorite program, eat dinner in the den, or stay up a little later than usual to help make the experience fun for your child.

Bribe your child: Buy a gift, wrap it, and put it in your child’s suitcase. Show him the wrapped present, and tell him that he can open it only when he gets to his destination.