There is an organization at my university called Replant. Every year since 1991, students have participated in a massive campaign to plant trees. Last year, 1400 students were involved.

Like your suggestion of planting the seeds of rationality, this undertaking comes with pitfalls.

I've heard cynical/hilarious stories of Replant groups who go to the same location, several years in a row, dig up the dead trees they planted the year before, and plant new saplings in their place. The (rationalist) lesson here is that there are places where seeds won't grow. Effort would be better spent elsewhere.

Also, as tends to happen with many in-groups, "Replant People" have acquired a reputation for being mildly self-righteous. I can see the same thing happening with rationalists trying to spread the dogma.

So, at the risk of straining the metaphor past the breaking point, planting the seeds of rationality is a great idea as long as you've found a nurturing environment in which to plant them, you can invest energy in guiding their maturation, and you don't come off too smugly.