1 MILLION percent support. i love the mockup and the fact so little is done about scamming on a site that kids use is really appalling.
not sure how much coding it would require or if it is even feasible, but it might even be a good idea to automatically bar dec 18th pets from being traded out/offered on for a certain amount of time (a few days to a week), with warnings like OP's mockup until the time is up. i know it won't fully prevent scamming, but it will actually give users a chance to figure out what their pets are worth without being bombarded with tempting (albeit unfair) trade offers.