When my daughter graduated HS, I filmed the procession, 2 speeches and all of the grads getting diplomas, the recessional. The reason I did all of the grads w/diplomas is that I gave about 20 as gifts to her friends. The chapters markers were the procession, speeches, the diplomas broken down into about 5 chapters so they could skip ahead to their point and not sit thru the whole thing.
I've covered both our daughters' college commencements. We host Int'l students from the Uni too and every year I make DVDs as a gifts since a lot of the students' parents cannot attend. After trial and error this is my recipe:
Outside shot of the venue
Inside shot of the Univ logo - usually start zoomed in and slowly zoom out to see that section of the gym which usually has the platform.
Inside sweeping shot of the gym
Procession of the beginning portion (about 10+ minutes)
Procession of their field, each dept has their own banner, and I get the whole group. Looking for our students and following them to their seats.
Procession of the Platform Party
When I edit the above clips, I use the audio of the beginning for the full length, the video of part of the beginning and the video from their field clip. This way the audio stays the same through out of the Pomp & Circumstance music.
Flag Ceremony
Chancellor Speech
Student Speech only if one of their peers from their dept.
While the other speeches are going on, I get zoomed in shots of our students. I use this to cut into the Chancellor Speech segment later on. Just be sure they aren't on their phone or talking to their neighbor.
Conferral of Degrees - The announcement by the Chancellor and the students move their tassel from one side to the other.
Walking to get their diplomas on stage and the handshake and then walking back. Now I only take one camera so I may not get everyone walking up, but may keep the camera on the stage for their group. Sometimes we have more than one student graduation. Last year we had 3 in 2 different fields. This year we have 3 in the same field. Some years we have had 2 ceremonies in one day! There are 4 ceremonies over 2 days.
The school song.
The Recessional - usually the platform party leaving and then shots of our students.
Outside photos/videos w/friends or family. Inside photos/video with the platform in the background.
I grab photos from their Facebook page to add into the ending of the video (with permission) These are usually candid shots in the holding gym they take with cell phones.
My advantage is that it is the same thing each year at the same place and I know where to sit. We aren't allowed to walk around anymore.
I would check out the venue and find out where they are setting up the stage. Where is the sun coming from and where is your son sitting. The higher up in the stands is better to shoot over heads and zoom in.
I have used a monopod, but last year I used one with chicken feet and that is even better. If you do use a monopod rest the base against the inside of your foot and knee. Last year I had audio problems in a 2 minute portion. Seems it was user error. I didn't lock the external mic down and it got jostled when I was resting the cam across my leg during the down time. At least I did figure it out before it was too late. John 2sheds saved the audio for me.
Good luck! Congrats to your son!