Soccermom,
First off, congratulations to your son! Getting a nom is not easy; he showed the world that some people in important places thought very highly of him.
It sounds to me like your son wants some information on the "Now what?" part of the equation, and wants to know where he stands in regards to an appointment.
Now, should your son contact his B&G officer? Well, here's my opinion and advise: Have your son call the B&G officer (at a respectable time, such as after dinner or early afternoon. Use the contact numbers they gave you.) Let them know the good news that he received a nom (they probably are aware, but since they haven't contacted you, you have no way of knowing this). Thank them for their help and time so far and for getting him to this point (nominated). Ask the "Now what" questions, such as, "is there anything else required of me?" or "is my packet missing anything?". Ask the "so, when will I most likely hear some further news?" question. When they are done, THANK them again for their time and all they've done so far.
The B&G officer may be doing this as a volunteer on their own time, but I'm sure they all are happy to hear from prospective cadets who have good news, good news they have had a part in helping them get! And, from the impression I got, they LOVE to help out these prospective candidates, and are happy to take these calls, answering the important questions. They understand how important it is to the propsective cadets and their parents, and are very patient with all the questions.
Bottom Line: Call, be polite, be respectful of THEIR time, and be thankful. And I'm sure the B&G officer would be happy to hear your good news...
Bullet