Isn't the WTS tax-free anyway? So what would be the point of these gifts then, as a tax-return on an already zero tax?
They shouldn't be.
Policy statement
The courts have held that an organization is not charitable in law if its activities are contrary to public policy. An activity cannot be held to be contrary to public policy unless there is a definite and officially declared and implemented policy (that is, found in an Act of Parliament, a regulation or other publicly available government document of any kind).
http://www.cra-arc.gc.ca/chrts-gvng/chrts/plcy/csp/csp-p13-eng.html