Creativity is limitless and different for each people. I think we just need to give them enough knowledge how to develop your ideas and principles of design. For me, I believe that delivering knowledge is better with series of workshops or group activities. Gathering all the geeks for information session with series of related activities might work well. As designers we tend to give experience to other people through our design. This time, the challenge is to design gathering session with all the geeks and then let them gain knowledge from the activities through their own understanding. In the end, even geeks can be creative to make their own designed interactive kiosk.
For example competing on a group might be interesting for the geeks. Then they started to interact with each other and they will understand what interaction means. What is interesting and what is not. What is engaging and what is boring. To make them compete also useful to make them think like a designer. being perfectionist through what they create. As a designer that wanted to teach other, we must be able to copy our design thinking and methodology to other.
After they were able to think like a designer, the next step is to educate them with the theory and principles of design for the interface itself. About color theory, contrast, materialities, fonts, visibility, etc. We need to feed them enough with theories of design they can use to develop their idea.