Packing - Kids
Kids come in two categories; those that care immensely what they wear and those that couldn't give a hoot as long as it's comfortable. Because you're the one that bought the ticket you get final say in what goes into the suitcase, but make sure to include your kids in the decision making process. You don't want to ruin a beautiful day in Paris because you have a child refusing to wear what you've packed!
Your children will need clothes that wash easily (or at least hide the dirt well), are comfortable, and look nice when you show Grandma the pictures when you get home. The same rules apply to kids that apply to adults - don't take more than you need and plan on doing laundry while you're on the road.