First of all welcome to the group.
I have heard a lot of good things about Dr. Buckmiller you are in very good hands.
I have facial PWS and am going blind from detached retinas and other conditions.
I know exactly what your son is going thru. Even though I am 23 I have been down that road already. For a look into the future it will get better. Elementry school was always the hardest part of school. After that the kids will start to grow up a little and will except your son for who he is if you stay in the same school district. I would say moving around would be the hardest thing for a child in your sons position. (just something to think of if it ever comes up). As far as the self-esteam thing at school, teach your son to let the comments role off his shoulders or just ingore them. The comments, pointing, and staring has been something I have had to live with my entire life and will for the rest of it until technology gets better. Talk to your son's teacher(s) and see if they can provide him with a little more positive feedback on a one on one bases. Not in front of the other children that will only make him stand out. You do not want them to treat him any different from the other kids because it will make him feel like an outsider. I have seen it with other people with a vascular birthmark.
If you are interested I did write a paper on social issues. It is about things that worked for me and things the might have if my parents would have done it. It is a mixture of my childhood education and psycology classes I took in college and my personal experiences put together. The paper is on my website at www.hankspws.com
at the bottom of the page.
I hope everything goes well with your son's treatments.