First, do not apply ED anywhere if you want to go to USNA. ED means a commitment to the school and dropping all other applications if accepted. There is no Service Academy exception. (My personal view is way too many people, ( including my own daughter) play the ED game, trying to get into a reach school by applying ED.
Second, nobody at 18 years old knows whether they are going to have a successful Navy career. In fact, many don't know until the day they retire -- each assignment has its growing responsibility and pros/cons. Someday you wake up at 20+ years and say, wow...I never really knew if I was going to make it a career . As a BGO, all I look for is the commitment to keep an open mind, and strong desire to serve for that initial commitment. (Face it, the Navy /Marine Corps needs a whole lot more LT's/Captains than they need Admirals) .
Finally, to go anywhere in finance these days, an MBA is important. I am a strong believer in the benefit of serving in the Military, or at least holding a job for a few years before going to grad school. The maturity and real world experience is important, as is the ability to lead and manage people. I got out after 7 years and went to law school. I've worked with finance people of all levels, and there is nothing worse than the know it all 24 year old, fresh out of MBA school , who can spout off a bunch of big MBA words but really doesn't have any practical knowledge or know how to deal with people. (Well, maybe one thing worse is the young lawyer with same background
).
Bottom line, you will never regret serving in the Navy or Marines Corps. You may serve 5 or 30. If you get out at 5, you will be more than qualified to apply to grad school, and will come out better at whatever you chose to do because of your service.
Good luck.