I would encourage you to interview several doctors, so that you can find out the different approaches and treatment philosophies they each have. No two doctors are the same, of course, and you may find one with whom you feel more comfortable and confident.
We interviewed a local dermatologist who could provide laser treatments but found out that treating children with PWS was not her specialty (or even something she did that frequently). We decided we would feel much more comfortable with a doctor who had greater day-to-day experience in treating pediatric PWS. We now have to travel a little bit greater distance to a different dermatologist, but we feel much more confident that he is the right match for our daughter's needs.
Sometimes it may seem that doctors are in positions of great authority and we must go along with whatever they say, but don't forget that as parents we are equal members of the health care team for our children. Our kids depend on us to be their advocates and find the best care for them.
I'm sure you'll be able to find an appropriate doctor, whether dermatologist or plastic surgeon, that you feel good about. Good luck, and blessings to your family during this process!