I was in the same boat as you. Taking classes part-time, as far as I can tell, will not affect your chances at all. Med schools are taking into consideration how well you're able to balance everything else in your life, so if you were doing it due to work, ect, they should still be able to make a decision based on that.
I agree, take the plunge into full-time when you're ready. Good luck to you.
PS, stop by my site and let me know how you're doing. It's nice to find another soul out there in the same boat as me 🙂