Xenon - thanks again for your help.

Thought I would paste some of the inspector's email to me this morning
"I wanted to let you know that all your efforts to assist paid off. I put the Regional Police in touch with the family of the youth who posted those messages on your website. The investigators contacted me to let me know they were planning on attending that evening to speak to the boy and his parents.
I do not know what the final results were, however I am sure they attended and took some type of action to evaluate the situation. I will let you know more within a few days as to whether it was actually a threat or not. The matter is no longer a concern though, and we can be more relaxed regarding the kids going to school today.
Thanks again!"
A good ending to a bad situation!