Behavior is the number one thing for me. Without behavior they will be missing out some of the most important things. A lot of this is higher level/sciency stuff, but if you want some ideas check out this book we used in CSU's equine science bachelors for the intro class. It is super expensive but there is an awesome 7-day free e-book trial so you can browse through if you want some good ideas for topics and some helpful info. Good luck and thanks for doing this... its super important and most peple miss out on this in lessons.