does undergrad matter?

They do care about your undergrad to an extent. You would be best served going to one of the places you mentioned as having a great MBA program for your undergrad and then saving the MBA until you need it or want it later on. Columbia, NYU, and Cornell all place well to investment banks. Hofstra may have some one-offs, but you will have a much tougher time going that route. Also, you would be better off trying to get into a bank right out of undergrad than trying to join after business school. Much more risk, entering later in your career, and you immediately put yourself on a track where upward has golden handcuffs and lateral moves come at massive paycuts.

My advice to you would be to keep your GPA where it is and enjoy high school. Study hard for the SATs and go to a college that will make you happy. You CAN find a balance between attending a school that has an opportunity to get you a job on the street while also having a great social scene. A lot of kids will tell you that you need to go to a target and hit the books super hard for 4 years... while you can't slack off during college, you don't have to approach it that way. Many of my friends across multiple firms went to schools like Boston College, Wake Forest, Indiana, Texas, etc. Yes, I also have numerous friends from Harvard, Wharton, Yale and Georgetown, but the kids I know who had the most fun went to state schools, and have the same job.

Just food for thought. There are a lot of factors at play, including how your education is being financed (i.e. are mom and dad footing the bill or are you paying your own way). Since I had to pay for school, I went the route that was likely to provide me the most social fulfillment and also the best return on my investment, and I couldn't have been more pleased with the way it turned out. Ultimately, luck is going to have a lot more to do with where you end up than you will probably care to admit, but you can increase your chances of getting to where you want to be by being humble, enjoying life, and not trying to control things you can't.

Hope that helps. Enjoy high school and college... I think a lot of people, myself included, would love to be able to get back some of the carefree days of college partying. Whatever you choose to do, enjoy it and make it your experience.