Children should have the right-of-way (except for cases of malicious intent) on public play paths over aging Baby Boomers and GenX codgers on wheels.Fine with me, but until that's spelled out on the sign, we're both out of luck.
You still miss this crucial point: "Who cares what they put on the sign?". It isn't the law. It is non-enforceable. Please explain how it is enforceable.
Look at it this way; how would you feel if a bicyclist came barreling down a sidewalk at you, screamed for you to get out of the way, they took a tumble, broke an arm, and sued you?