A friend of mine did IB in high school, but I don't have much personal experience. I'd be happy to talk about presentation ideas.

My standard advice for short-form presentations is to try to paint a picture that something more is possible; I've found Bishop and Trout's Epistemology and the Psychology of Human Judgment to be a good example of this. The book basically outlines the case that psychology can inform philosophy, and that coming up with superior algorithms for actual practice is better than debating labels. The inferential distance to actually explain rationality is much longer than 20 minutes, but it seems like 20 minutes is enough time to explain that rationality exists.