If you're willing to make some sacrifices I'm regards to your personal life, you will be able to juggle all that at once. I'll be honest, you'll end some pretty thick skin to pull it off, but after a few months of struggle your time management skills will be amazing. I myself found it worth it because I'll be used to a really busy daily life schedule in medical school. That's one thing that taking time off school can't always teach you.
However, I would totally advise against studying for the MCAT during the school year. If you're not rushing to go to med school right out of college, taking a year off is completely normal. It's amazing how an extra year of life experiences can make a good application into a great application. At the end of the day, you'll be a practicing physician for 50 years more or less, so know this isn't a race and taking time off isn't a huge deal. I've read it on various message boards that not a single student that took time off regretted it (unless you did nothing productive). It's all about equilibrium and how much YOU think you can handle. Best advice I can give you is to use your calendar on your phone daily to plan stuff and hang an identical calendar on your desk so you can see what you're walking into every week or month. I don't want to give my life's story, but I'm actually in a similar degree situation as you as a commuter student managing various research/volunteering/part time job, and you would be surprised how much you can handle. It's all about thick skin and equilibrium! Hope that helps!
