You could also argue that taking organic over the summer is MORE challenging, due to the fast pace. If you fall behind you could be in big trouble. So it's not clear to me why taking orgo over the summer would be looked down upon by AdComs, provided that you take the course at a university that has a reputation better than or similar to your home university. I took most of my pre-meds as a post-bacc. To save money, I took as many as possible at a local state university (that fact has come up in several interviews, and my interviewers all agreed with my rationale). Furthermore, I called the Harvard Med Admissions Committee before starting all of this and they said - as a post-bacc - that taking classes at a state school to save money was totally fine. That said, I did opt to take orgo at a more prestigious institution (that happened to be private) to prove to myself (more than to AdComs) that I could do well there. To tell you the truth, my interviewer at Yale questioned my decision to take the class at the private school because it cost so much money!
Good luck with your decision. Do what works best with your schedule, work hard, and be prepared to explain your decision-making process to an interviewer. I think whichever option you choose will work out well!