Congrats on the progress.
1) Ask anything you feel relevant to the process and you feel unsure about. Scouts' intentions are to get a feel for your son as a person, as well as his interest in potentially playing professional baseball for their organization. At the same time, a scout is also trying to make your son (and, as an important extension, your family) comfortable with the process. Scouts realize that it can be somewhat overwhelming at times, especially when there are uncertainties involved. I usually describe the interaction as "respectfully informal," as both sides are attempting to feel professional comfort in one another in a personal setting. Be respectful of general professional boundaries, but don't hesitate to ask questions you truly wish to ask.
2) To be honest, I'm not sure what you mean by this question. Scouts wouldn't be making home visits to a draft eligible player if they weren't potentially interested in drafting him.