[Polybius]

Wouldn't be enough to put up a Caution sign indicating children at play?

Not really because you expect normal children to react in a normal way. It is an "Expect the Unexpected" warning sign.

[netmilsmom]

How about a nice "Parents watch your Autistic Children" sign?
Rather than hoping a driver will stop for a child with special needs, I would rather not take the chance with my child's life.