I don't think stagemom3 meant to discourage you from auditioning at any of these schools. I think what she means is that at schools where it's basically assumed that if you get in, you're going (very few turn down CMU or UMich), they don't tend to offer very much financial aid. Basically, they know they have you. Cynical, yes, but the whole applying-to-MT-schools taught me a lot about the business side of things. Some schools do talent scholarships, but many larger schools will probably give you financial assistance in grants based on academics in high school, so that 3.7 gpa should help you a lot.
As a current MT student, I can assure you that this major will completely consume you. In a good way, of course. You'll be busy with classes, homework, practicing, recitals, performances, etc., and it makes many things (including a double major) nearly impossible. This is in reference mainly to more intensive programs; perhaps at a smaller school, arrangements could be made to double major, but it might not be the best idea for your health and sanity
I agree with the other posters here that you should do the individual nitty gritty research. Even though you're not in the potential MT class of 2013, join the group on Facebook (if you're on there too). There are current 2012 MTs that could help you out with specific, personal experiences. I know one girl who goes to Millikin who could be of assistance!