When I was in that situation I had the students do more. I gave them topics to research that pertained to the course material and had them give mini-presentations. I have also had debates/panel discussions and I gave them computer time to research. The next time I teach the class I am more knowledgeable. In my experience, students enjoy the debates/discussions so much they don't realize that you are doing it because you don't have time to prepare. Also, I talk a lot about what I know best and have the students do the work on the topics I am less familiar with. I also use field trips and guest speakers to fill in my gaps of knowledge.