After a year and a half in university I enlisted. I told my folks what I had done over diner. They turned pale, swallowed, then asked my why. I told them it was because I wanted to. Now for them the shock was real, Vietnam was in full swing and until I told them I went Nuke, visions of what they saw on the evening news was flashing through their heads. They did not like my decision, but eventually accepted it. (when I finally shipped out)
So if you want to be an operating engineer and get your hands dirty, enlist and go for it. Otherwise, if it is a nuke career you want, get into an officer program now and finish college. I always found it more rewarding to hear "Yes Sir", then to have to say it to a junior officer still into his six years of earning the salute.
I left after my enlistment was up as an ETR-1 (yes, back then ETs were either radar or communications and were tested on those specialties, not reactor instrumentation and control etc) I was 25 years old and married when I went back to finish my degree. I became an accountant and never second guessed my decision to be a nuke or to enter the business world.
As long as you excel, your mother will get over it.
Oh, if you think this is hard, just think of when the time comes and you want to get married only to find your mother does not approve of your choice.
Life was given to you by your parents, what you make of it is entirely up to you.