First of all welcome to the group.
Have you done any research on KT syndrome? The reason I ask is because a lot of people I know that have PWS on the limbs have KT. The difference in the size is one indication that I heard you talk about. I have a condition with my PWS called Sturge Weber Syndrome. In which KT is linked to that as well but given the location of your sons PWS I do not think he would have this, but SWS sites have a lot of info about KT as well.
One thing I would suggest is to contact the KT and the PWS experts on the front page of this website. Send them pictures and see what they would recommend about the butcheek area. Remember if for some reason you ever become uncomfortable with the current doctor you are seeing you can always get another opinion.
For treatments I would suggest the least amount of sun exposures before and diffently after. If he is going to be in the sun use 50 block on the area where his pws is because the sun will make the laser treatment less effective.
You can see before and after pictures of what laser treatment has done for me in the past 19 years on my website www.hankspws.com
. Being that I have a very dark purple birthmark it takes longer for the laser treatments to help. The lighter your sons PWS is the easier it will be to treated.
For the stares plus everything else. Being that I have a facial PWS there are a lot of different. I have learned how to not let the comments get to me. In so speak let them roll off my shoulders. It still bothers my friends when I am around them and people are staring at me they get affended. If you are act in a negative effect with people and your son sees this he will do the same. I personally always choose the educational side of it. Teaching people about it makes them more comfortable. on my website I wrote a paper on social issues if you have any interst in reading it, it might help.
I am sure others will chime in and give you the parent prospective. If there is any other questions you have please let use know we are here for you.