My congratulations as well. My daughter was one that got a surprise appointment and she had never been to Annapolis before I-Day. She is now in her second year. She has had company mates DOR (discharge on request) and the pandemic hasn't helped. She, however, is as firmly committed as she was on I-Day.
She idolizes my dad who served in the USMC in Vietnam. Ironically, he does not speak about his service. But those circumstances obviously changed him in ways that makes him her role model. So there is that aspect. There is no one amongst her aunts and uncles that served, nor did either me or my husband. But that service is something that attracted her.
While she always knew that she was going to go to college, she didn't get serious about it until the end of her junior year in high school. We, like you, were prepared to support whatever decision she made and made it clear that it was her decision. She was actually applying for the Naval ROTC scholarship and the APPLY HERE button had her completing the pre-application for USNA and that wasn't until the beginning of the summer after her junior year. So you can imagine even her surprise when she got her nominations, her BGO approval and then the appointment. Her question at that point was HOW? She had good grades, but others had better. Her test scores were above average, but others had better. She didn't have all the AP courses that others had. She was a high school varsity athlete in several sports, but wasn't good enough to play at the D1 collegiate level. She held leadership positions and volunteered, but then so did everyone else. We had her ask her BGO and those that wrote her letters of recommendation what in her character stood out to them such that she would succeed at USNA.
My suggestion to you is to first have your soon reflect on why he completed the application and how he thinks being an officer in the US Navy (or USMC) can help him meet his long term goals and how he can better the Department. Then have your son engage in a conversation with his BGO and his references -- they obviously can see something in him puts the USNA in a position to help him achieve his potential.
Engaging in all that helped my daughter to realize that for her USNA is the best thing that could have happened to her, but also realize that it is also not for everyone.