How fortunate you are!
Is this a class in a high school?
I most definitely agree with
Bęthberry because most of the time questions that people have about the past and future of the characters in LOTR is what leads them to the Appendices. But, yes, stay with the basic LOTR related info. This is most definitely not the time to get into the more complicated Silmarillion related matters (but I guess you could tell a little about the history of Sauron... but, yes, that would be getting a tad bit complicated). I don't know about the languages, but if the group that you are teaching shows an interest in it I guess you could talk about it a little.
Good Luck!
