HELP! New grad night shift & a mom! How to do it all?

I accepted my first position as an RN on night shift in a med-surg/ICU unit working 7p-7a and I am very excited but at the same time extremely nervous. I will be on days for a month but then will transition to nights for the remainder of my training and will stay there. My question is this...

How do I meet my physical needs, be an effective parent/wife and an excellent nurse simultaneously on this schedule. I am most concerned about juggling it all. I have 4 children (ages:12-8-8-2) and last time I was on nights (worked 3p-4a) I didnt do so well and gained a TON of weight. I was also in an abusive marriage at the time and that is now behind me. I truly want to be successful at making this schedule work with minimal impact on my children and my health. I do have a great support system and a wonderfully supportive husband but still I worry about meeting the needs of my patients, self and family without gaining weight, losing sleep, or neglecting my own health. Any and all advice is appreciated.