I feel your pain. We recently had a chocolate lab, and they are a little different from other labs. He is sweet as can be, but we learned a few things about that breed in having him. #1-You have to take her through obedience class to (a) establish dominance and (b) learn how to control her. #2-They are very mouthy: chewing, licking, biting. One reason for #1. #3-The more attention you give her, the better behaved she'll be. #4-They don't outgrow the puppy stage for at least 3 years. Since your parents saw fit to decide this, get their involvement in training her and coordinating the interaction between her and your son.
They're great dogs, both as protectors and companions, but they do take a lot of attention at first. Since you're going to school and being a mom to a son with special needs, I know you don't have that much time. All the more reason to get your parents involved. I think, eventually, Lady will be a great benefit for your son and his ADHD because working with Lady will teach him discipline and self-control.