Haha, yeah, unfortunately this was very true in my case. I think it’s good that you’re thinking about it, but please don’t let the thought of college completely dictate the next 4 years of your life - don’t be that person that only does activities/certain classes for the sake of your resume or your transcript.
As already mentioned, piano shouldn’t go on your resume - especially considering that you quit at a very young age. Violin and clarinet on the other hand - that’s good, assuming that you intend on sticking with it.
At least from what I noticed with Ivy League applicants from my schools, they usually have some amazing accomplishment outside of school - I can’t give specifics (b/c they can actually be looked up easily) but their accomplishments were really impressive. They usually have high GPA/high SAT scores, with a rigorous course load, but they usually aren’t taking ALL AP classes junior and senior year (unlike certain other Ivy League applicants from my school). So just remember to keep your ECs strong, as well as your course load.
I third the scholastic suggestion - and you should look around for other contests that you could enter your work into. I think your passion for writing is great!
Good luck! 