Writersoul- I run a branch of a well known kiruv oganization in New York. I have the opportunity to meet and learn with many completely irreligious Jewish children. One thing I have have noticed is how the high school age girls in my program are able to teach the parents of the secular girls so much.
The non-frum adults know as little as their children, so it’s really not hard to teach them things. Even by just dressing tzniusdig in front of them, or teaching them how to daven and make brachos, you are making a huge difference in their world.