OP, congrats on your accomplishments thus far!
Adding something this coming summer in terms of research that helps demonstrate your passion for physics and computer science would be a great addition. Plenty of options out there but I’ll put a plug in for the Summer Science Program (SSP) since I’m most familiar with it in particular – the astro sections combining orbital mechanics with CS (in Python) could be a good fit for your interests, and some of the schools on your list (MIT, Caltech, Harvey Mudd) have close ties with and actively recruit from the program. Good luck!