You can report to your Province but you can also report to CRA. Chances are they not writing receipts for all these kids with SIN number. CRA does warn when you report that they not give your name but if you close to illegal provider and know them, they might suspect it you. Since you not know them, you have no concern about them getting annoyed with you.

To report to CRA, you call http://www.cra-arc.gc.ca/gncy/nvstgtns/lds/bfr-eng.html. This department does not have caller ID and they do not take your name but they need illegal providers name, address, telephone number if you have it and any details you can provide.