Columbia has a rather small mechanical engineering program. It's considered a very good school overall, though slightly less so in engineering. It is right in New York City, a huge business and finance hub, so you'll be easily able to get in contact with potential employers in the city. It's fairly common for people to transition from mechanical engineering to business/finance. Most employers tend to give a lot of credit to the school where you got your most recent degree, so you'd have little difficulty getting a fairly well paying job with a mechanical engineering degree from Columbia. Before you graduate, paying tuition might be an offer though.
That being said, you seem to be receiving acceptances to a variety of programs and are doing a lot of things to improve your resume. If you were to apply to schools in a year or two, you would probably receive some pretty good offers.