part of me thinks there is a bigger issue if you are that afraid to bring it up. But that isn't what you are asking about. Take some time and get all your ducks in a row so to speak. Apply for a pell grant, find out how much classes cost and if you can get any other help, free help, so that you are not paying out of pocket or taking out loans. Then make sure you talk to the school, make sure you know what it will cost if anything (sometimes you can get money back, if your grants are large enough). get a start date, and basically do everything but actually enroll.
At that point approach your husband, tell him what you want to do and how it can work, don't worry about years from now and clinicals, who knows where either of you or the kids will be in life in a few years. Having all the facts and going to him with them, rather than going and asking permission and for help, should help him see that this is really important to you.
good luck.
and just because i have to say it, if you are that afraid of him, and he is that controlling, well then maybe you should think about getting a divorce and then going to nursing school.