I definitely agree that you should give a basic explanation of "how" to become a doctor. Most kids haven't the slightest idea outside of it taking a really long time. In fact, I wasn't fully aware until I came so SDN, so that would probably pretty helpful.
You could also try to spark some interest in the kids, maybe asking them if they've ever considered the field of medicine...explaining why you decided to go for it (like working with the human body, other people, etc.). I know one of my main motivations for trying to do this is because I'm absolutely fascinated with human anatomy and medicine, especially how far the body can be pushed (hence my love for sports medicine). It's probably the coolest thing I can imagine doing in my life, so I'm ecstatic about it.
Good luck!
