"Please insure that children are not left unattended"

[Caz10]

Shouldn't it be ensure? Or am I just not getting enough sleep at the moment??

You are right, unless the people who wrote the sign are selling insurance...

Yes ensure

Is it an insurable risk?

it was one on of these "official" signs you can buy from hardware stores etc, in a trade place that sells tiles...I was annoyed enough at being there on a Saturday morning without seeing that!

maybe an American sign? US English is insure not ensure