Here is my opinion - for what it is worth. My child has a form of dwarfism. No service dog. When he was 4 years old and only 24 inches tall, people would ask his age. Sometimes we would get strange looks, or rude questions. People sometimes used inappropriate words, which I felt the need to correct. I'm sure my responses depended a lot on my mood and the situation. I handle strangers differently than say - teachers and classmates. Teachers need to understand my child's health situation and needs. For younger kids, I kept it simple - "He is small, because his bones don't grow like they are supposed to." Now that he is 11, he can handle these situations on his own.
It seems to me that a dog could help. I know there is a service dog called a "social bridge." The dog takes the attention off of the person. It would be the perfect opportunity to talk about what the dog can do - not what my child can't do, or needs help to do, or any medical specifics. So, if the dog can bring you a cold drink, people will be impressed with that. Who wouldn't want a dog that could do that? And does it even matter if that is not the dog's primary purpose? I have such a warped sense of humor, I would probably come up with some crazy stuff that this dog could do - whether he could or not. It would be so much fun to mess with people's minds. Through it all - you have to have a sense of humor, or you just go crazy.