I agree with the suggestion that you have backup plans for your backup plans, and then back up THOSE plans. You need to have a nice big group of people who can help with your kids, be available if you can't go pick up a feverish baby from day care because you have a final exam, etc. Student nurses who have kids are a lot more common than I would have thought, in my experience it seems like MANY new moms have their first "real" experience with nursing when they give birth and just want to be the ones providing that care, whether in women's health or anywhere else in the hospital. It's also a great career for a mom, the hours can be so fantastic for a parent (seriously, where else can you work 3 days a week and make a comfortable salary?) - so you'll probably meet other moms in your classes. I wasn't ever able to do this but I think it would be AWESOME to set up a nursing student playgroup, so the kids could run around and have fun together while the moms studied.
I am militant about my kids bedtimes, I have been since they were itty bitty, and that has helped me a lot. I KNOW that if they're in bed by 8pm, I have at least 2-3 hours of good, solid studying time that will be mostly uninterrupted. We also do "homework" together - I study and they draw or work on school work.
One other tip, if your instructors are really strict about cell phones and you (like me) are not willing to be unreachable in case of an emergency, I would let them know on day one that you need to keep your phone on vibrate in your pocket, just in case. I have set my phone to vibrate if my kids' schools call, but anything else is silent, so if I get a call I know it's about my kids. That has been helpful for me, too.
Good luck! It will go by so fast and your whole family will benefit from your new career.