I agree with PPs that you certainly should be blunt.
I am clergy, and our believers share much. BUT we know
to let it go, to not make anyone uncomfortable, to not push.
You checked the literature out, as you informed them.
Some just want to convert then teach and inform. Maybe
their zealousness is admirable, but their tactics are not.
You can tell them the basics as others said, "No thank you,
meeting cancelled, don't come by again." And let your minds
be at ease.
ETA: we posted seconds apart but "Vacuum cleaner salesman...." excellent!