That's the most irresponsible thing I've ever heard of. How about the developer providing parks and playgrounds for the kids to play safely. I wouldn't let my kids play on ANY road, no matter how quiet or how many signs there were.
There are a few parents in my neighbourhood who seem to think it's OK for their kids to set up cricket stumps and skateboarding ramps in the middle of the main road. When there's a park 50m away.