My kiddos are singing in the original Latin. We also add in hand-drums (played with a soft mallet) on the half note beat, tambourines (they play the rhythm of "Gaude" only) and recorder (little over-achievers of mine). These instruments really give our performance an authentic sound.
I made a little page for them to put into their interactive notebook. See below:
I've been going over this song for about the last 5 or 6 lessons. We discuss a fact each lesson. I've created a PowerPoint for that (if you'd like to use these slides, you can copy and paste the pictures or email me at firstname.lastname@example.org and I'll send them to you):
The students have also enjoyed watching and listening to other musicians perform this piece. Our two favorites are: