Extracurricular Help?

I am currently a sophomore in high school, but I am not on any academic team (scioly, math team, etc.) and I’m afraid this will look bad for college apps. I am in marching band (concert band 3, highest level in my school) and I volunteer at my local hospital. I will also likely acquire leadership positions in both, such as section leader and department leader. I was also in ASB this year, though I will not do it next year. My academics are rather strong (4.0 unweighted, most rigorous AP classes available). I’m just worried my lack of academic teams will hurt me. I plan to major in computer science, and I need help finding a related extracurricular. Would creating a mobile app help? I’ve tried finding cs-related internships within the southern California area, but I have not been able to find any that accept highschoolers.