From biography.com, here's a two-minute video; and from National Geographic, some of their always-stunning photos depicting with captions his journey to China. If your child is just nutty about Marco Polo, there's a PBS documentary (1 hour, 25 minutes...) on two adventurers who follow his journey from Venice to China and back--which I have not watched. And for the rest of you who I'm sure can't get enough of him, there's an animated video to buy designed to build character in kids. The two-minute trailer might be enjoyable to your kids!
Here's an interactive map of his journeys, complete with sound. If you're looking for more resources, click here.