Ok here's an idea, you find leads of houses in your area with a kid whose birthday is coming up and send them flyers. You're a dev guy this should be up your alley. $1 each with Postgrid API or do it yourself and it's the cost of your time + stamps + papercuts. Where do you get those leads do you ask? That's actually a good question and I'll need to get back to you on that. Make sure to put a QR code on the flyers.