Calmom and Nancy, one very important thing to point out is the fact that your sons are being recruited and it is only August. It is not unusual for DIII's to really begin recruiting aggressively in October because that is close to the time the DI's are ending. DIII coaches know they can waste a lot of time and energy recruiting players at this point who end up with DI's.
Another clue for you is how often and how consistenly the coach calls. If the same coach calls once per week, every 2-3 weeks, that also is a good indication you are high on their radar.
Most importantly, do not be afraid to ask where your son fits with them and press for details. This is the only opportunity you get. Do not let it overwhelm or confuse you and your son, although it can seem that way now. Also, have confidence that as the year progresses, the visits will allow your son to become comfortable with some schools/coaches and rule out others.
Bottom line, you have every reason to be optimistic based on the number of schools already showing interest and the fact your sons are very good students. My son ended up just fine at a top DIII where he had a nice career and got to play in the NCAA regionals on two occasions. His first contacts did not come nearly this early.