I am going to assume that FutureAviator_USNA understands all the academic requirements for USNA. Sports, PT score, and activities are things to work on.
I highly recommend U.S. Navy Sea Cadets, as it is more military focused than Boy Scouts. Sea Cadets is also individual focused, so the cadets can attend summer and winter trainings that appeal to them. My son loves Sea Cadets, and wishes he joined earlier (HS class 2025). Work out on own to max the PRT standards, and will easily max standards. I am not sure about USNA, but NROTC is 75 push ups, 3:25 minute plank, and 5:20 mile.
For sports, four year high school team sport is important, and captain in senior year is preferred. Individual sports can show excellence but not leadership. My son attends a charter school and is on track to be captain of basketball team junior and senior years. We are happy he is in a charter school, as our local public high school has 3000 kids and basketball is filled by AAU all-stars, so most kids can't start in basketball (football and baseball as well).
Scholar, Athlete, Leader!