I have given some lessons (most of some composers) but I'm not an expert.
After reading the book they should have quite good grasp of the peoples of 3rd age so you don't have to worry about appendix F so much. The different calendar systems of M-E can be really confusing so I would pay less attention to that.
I myself am very interested in the different languages and tengwar writing system but I think that your class may not share the same passion for appendix E as I
I think you should focus on Arwen&Aragorn and the history of Gondor and Rohan. You could also draw a timeline of the early 3rd age and it's most important events. Then you could explain them a bit (some pictures could be helpful too).
From my point of view Firefoot's and Fingolfin's advice were good. All the best with your appendix lesson!