I'm on a very similar path as you. I am currently finishing my B.S. in Individualized Studies through Charter Oak State College. My concentration is in "Manufacturing Process Development & Project Management". Within this I am taking all of the upper division project management classes offered as part of the undergraduate certificate, which is certified by PMI to prep you for the test. In the end I'll finish my degree, get the certificate, and be ready to sit for the PMI test all at the same time.
Anyway, one more thing to consider is that the time spent getting those 30 additional hours required for that second major would probably be better spent on graduate level classes in the long run.
Danny