Just maybe, you've helped them to take a first step toward becoming true citizens of the world. Even if they grow up to be intolerant xenophobes, they still had fun. And so did we. After all, one of the primary pleasures of parenting is having an excuse to do kid stuff and to see Old World treasures from a fresh perspective. To our son, Versailles looked like the dream spot for a paintball fight.
Kids get lonely with only adults around.
For siblings, travel can strengthen ties. There was almost no squabbling, maybe because the kids really had to count on each other. They actually acted like, uh, friends. It made life easier for everybody to let the kids have their own hotel room to share. Respect that simple fact and your vacation will go more smoothly.