I only have one tiny bit to add. Kids get transplants much quicker than adults in the U.S. That is because they are prioritized by age. Please get him listed as soon as possible so dialysis can be kept to a minimum. Good luck!
You don't mention how your child has fared developmentally so far with the nephrotic syndrome. But since being on dialysis can permanently stunt the growth and intellectual development of a child, make sure he gets a transplant as quickly as possible. The wait should not be as long as it is for adults, because the medical system recognizes the urgency of children getting a transplant soon.
When I went on to PD I was able to go to school and remain a fairly active life. It also helps a kid grow better than if he was on HD as you are removing toxins more often. Fluid restriction are often less restrictive.
Full knowledge of what is happening should be given at all times as this helps understand why you take certain drugs and what might happen if you don't. As a 15 year old for me I was not to worried about things that could happen when I was 50 as this seems such a long way off to a young person. He needs to be aware that kidney failure is a disease that he will have to manage for the rest of his life.