Well, two points of view, both with points.
Believer:
Would not be possible to see well enough in the dark with these lenses to do what the children did.
Children most likely dont have enough money to get these lenses.
Contacts look slightly different than actual eyes usually, and the people would not have likely got the terrible sense of dread if they were normal.
It is relatively doubtful this many different children would participate in these events and want to apparently kill people for no reason.
Skeptic:
As far as appearance is concerned contacts could do the trick(although they wouldnt be able to see).
Could be fabricated story(possibly from a contact seller to get more attention regarding black contacts

), as there does'nt seem to be solid proof, and people who heard urban legends could fairly easily imagine someone, especially from the distance or in the right lighting, to have black eyes.
Ignoring paranormal laws they would not need permission to enter your vehicle/house. And by the way why would'nt they get someone outside of thir car or househole.
Not a terrible amount of reports.