The sign I've always seen was that "Unattended children will be sold as slaves".
There's a coffee shop in Pittsburgh that has a sign posted "Unattended children will be given expresso and a puppy."
That sounds cruel; the puppy could end up dead. But if you omit the expresso, it sounds like a good way to get rid of those baby kittens.
My brother says there is a used car lot he drives by every day. Last week, they had a sign that said, "Free kitten with every used car purchase". This week, it says "Free used car with purchase of kitten, $9,995".