OP, for SAs, including USNA, sports aren’t just an ECA, they are mandatory and a way of life. That means it’s really hard to be appointed without being active in sports and almost impossible to enjoy SA life once there.
Since you’re both both a homeschooler AND someone not active in sports during h.s., USNA will place great emphasis on your CFA. You can practice for that on your own. Lots of advice on this forum - just search for it.
However, USNA also likes to see sports on a candidate’s resume because it shows teamwork, determination, etc. as well as fitness. You might ask why your parents don’t want you to participate. Is it fear of injury? Maybe choose a sport where injury is less common. Are they afraid it wil
take time from your studies? Most successful candidates do it all - school, sports and ECAs. And you can d sports during the summer. Do they not understand the benefits - maybe ask your BGO to talk to them about sports and USNA.
Band is great but, in the eyes of USNA, it’s not a sport.
if USNA is important to you, try explaining to your parents how critical it is for you to be fit and involved in sports in order to be a successful candidate. If all else fails, set up your own workout routine and try to crush the CFA.