I had ever been like you before, in 2006, I started teaching english in an english private course in aceh. At that time most of my students had their different goals in taking english course. I had 4 different classes, teenagers, college students, lecturer and NGOs worker (after aceh being hit by tsunami in 2004, many NGOs came to Aceh).
As you said in your post, its quite hard to make all the students happy and enjoyed our class. I did all my best managing my classes, when I got teenagers class, I used to tell them some funny stories before I start teaching the lesson, and it worked. Then when I taught adult classes, I used to make some jokes, fun discussions, its aimed to make the class athmosphere easier to teach.
That what I can share a little bit about my experiences. But anyway, enjoy your class. Everything need process, nothing great is built overnight. Thanks you for sharing sir.