How much time will you have? If 45 minutes to an hour, you can give a pretty comprehensive "Orchids 101" talk. I tend to focus mostly on Phalaenopsis, since that's one that pretty much everybody has even if they don't have any other orchids. One little quip that might be helpful is one that I saw first at the SVO booth, but have used often. "Orchids are not cocktails... don't add ice!" Concept of "humid air" around roots rather than "wet", "Once weekly,weakly" on fertilizer ...
Take a look at the "Orchids 101" handout that I and the other Fascination of Orchids co-chair have developed over a bunch of years... It has a southern California spin so many points wouldn't apply, but there's quite a bit that is totally basic,
https://fascinationoforchids.com/culture/101.pdf
Another variation on the theme is on my own website
Culture Notes that may give you some points to think about.
Rereading your post, you only get 15 minutes. So I'd still focus on Phals, hit the most basic concepts of watering an epiphytic plant (air around roots important), light fertilizing. Appropriate light. That's about all you will have time for...
Enjoy!