Nice idea! If you're targetting the general public, I think rationality per se might be a bit hard to swallow (at once); maybe explain things in a bit more indirect way, for example:

• cognitive biases - there's plenty of material to choose from, and depending how entertaining you'd like to make you could use stuff like the 'invisible gorilla', some Dan Ariely examples, and so on.

• logical fallacies - take some well-known examples; again, there's quite some material to choose from.

• from there on, you could go through ways to think more effectively - e.g., how rationalists deal with pseudo-science. Maybe relate this to bayes' rule.

• now, when we have established what rational thinking is, you could discuss some more advanced topics, such as FAI.

In general, the general public knows little about these matters, you'd probably need a lot of light-hearted/amusing examples to convey our message (and avoid rolling eyes)