Hollie,
My experience of being in this community for a year is that facial AVMs are rotters to get under control.
I saw a BBC news article when I posted the original link below and found a YouTube video by a young girl named Nikki. She has quite an extensive facial AVM which might paint a bit of a picture of how your son’s AVM might develop. She discusses the treatments she has had. Her video is very difficult viewing for someone in your position, so do approach it knowing it is likely to show you difficult things but I hope it is helpful for me to share it.
You may be as well to communicate with the Facial AVM community here, as what you describe sounds very much like Nikki’s case.
http://www.avmsurvivors.org/t/nikki-lilly/16765
I hope this is helpful.
Love,
Richard