Bariatric surgery. He operates on me.

I want to get a bariatric surgery but I am under age and I am having a lot of trouble with my weight I have broken bones, joint issues and compress crack on my spine. The bariatric surgery asked me to bring my parents my father passed away a long time ago and my mother have her own health issues like b.p. and elephant foot she is also not much of a traveler she often gets sick in car train or flight. I have convinced her for my operation but it is really hard to get her to travel to city from village she is also uneducated and never been much of a outside person so she can't help me with anything. I wanted to know is there any kind of paperwork I can show to the doctor like a permission from my mother to convince him to operate on me. My cousin will be there on hospital when he operates on me.