Give the teachers material that they can present to their students in a class period. Don't presume ANY prior knowledge of the subject. Don't presume ANY prior interest in the subject. A large part of your talk, especially at the front end, should be motivational. Taking up to half your time to get the audience interested in the topic is not excessive.
Nothing awakens interest faster.
There are lots of good books available with all the information anybody would want. If they get interested enough in your leture, they will find out what you didn't have time to cover. Stick to the most fundamental topics you can think of. Start with questions that the audience may already have in their minds. For instance, introduce somatotopy by asking how they would know where you touched them if their eyes were closed.