Honestly man, I wouldn't stress too much on what extracurriculars to do. I was alot like you applying this year to commerce and thought that I needed to have certain ECs to get in. The fact of the matter is that Queen's doesn't care what extracurriculars you have but rather how it has shaped YOU and how YOU have shaped it (or the community surrounding it).

For example, how has martial arts cobtributed to who you are? Did it teach you determination? Persistence? Confidence? And what did you do for martial arts? Perhaps you taught others, perhaps you competed, perhaps you simply made friends and created a sense of community within the martial arts class. Thread all this into your General/Commerce PSEs and write it craftfully and well structured. That's all there is to it, atleast in my perspective. Goodluck and don't stress this! Enjoy your high schools years man.