The candidate should be the one requesting assistance, asking questions, reading instructions, and seeking requirements. I do not at all think this is too much to ask for a 16/17 year old.
Email: "Hello LT Smith, I had a question about x, what should I do in y situation. I have z circumstances that I'm worried about and would like more information. Thanks for your help. Sincerely, Timmy, Candidate # 625842."
I called people as a 17 year old with not much more phone etiquette than "Good morning, My name is x, candidate number y, I have z problem, can you help me?" I find it baffling that this is too difficult for any high school junior or senior.
Yeah, it wouldn't pass for proper correspondence as a midshipman, but I bet folks would be a lot more impressed by that effort than by something from a parent. They might even make a note of it.
The advice here is to keep competitive, and to remember that BGOs, Congressional staffers, and various Admissions officers can and probably do remember the candidates that were mature enough to handle their own affairs as well as those who were not. If the parent is tracking things and following up on issues for the candidate, that's very telling. A high school junior/senior taking all those fancy AP classes, and in all those club leadership roles, and he can't even keep a calendar to track something this important?
Maybe a better story: The congressional staffer for my district made it very clear she would toss applications if parents called in. She had no time for kids who couldn't make a simple phone call, and she really didn't care about whatever excuses. Work it out, make it happen. If your coach is more important than your nomination, so be it. If you have a stingy teacher that can't let you slip out to take a phone call from the Congressman's office about your future, figure out another time and let her know. It was a competitive district, she could afford to do that, and congressional offices are free to use whatever criteria they deem fit. So, if you were a parent in my district at the time that called in because Bobby was busy at baseball or whatever, you just robbed your candidate of a chance at a nomination from the Representative. Which was absolutely crippling, because getting a nomination from a California Senator was exceptionally unlikely. Undoubtedly candidates were sunk due to this policy.
Real consequences there, and partially why I take this position.