20 Questions Awards

We have a great feature on our website for kids called "20 Questions." After kids read their Zoobooks issue, they can check out this web page to find out how much they've learned. When they're successful answering the questions, they're rewarded with funny animal jokes. But we're thinking of taking this one step further: what do you think of offering them a printable Achievement Certificate instead--or in addition? We'd like to hear your thoughts.