TUTORIAL: How to write in Elvish. This is the most detailed and thorough I've seen. Also, check out a lovely book called "The Languages of Tolkien's Middle Earth". It explains elvish (Sindarian and Quenya), Dwarvish, and others. Written by Ruth S.
I actually would throw The Hobbit book at them and tell them they better read this. THEN, I would throw all THREE LotR books at them, make them read those, and OBVIOUSLY they will love it by then and we can watch the movies together.
Friendly reminder that Dean O’Gorman and Aidan Turner needed 47 takes for that scene: “Fili and Kili, at your service.” Because they didn’t manage to bow at the same time and because Martin Freeman was behind the camera making faces like this