One of those things that's become a cliche because it's true: traveling is a great way to do this, at least at an age when children are old enough to rationally process the new information to which they're being exposed. The more different the destination culture from the host culture, ultimately the better. Lived experience provides information very differently than written, oral, or 2-D visual transmission of knowledge - not necessarily better or worse, depending on the context, but definitely with a valuable variety of perspective.