Advice on adjusting to night shift?

I've been in EMS for six years but it was all transport and vast majority day works. I am now a parmedic and have just grduated from the fire academy of a major east coast city and i'm about to go on my mandatory 2 month ride-a-long for my medical command with the service. There's a lot to adjust to here - new work load, new work environment, not to mention adjusting to my skills as a paramedic. But on top of that, my ride-a-long is going to be on the night shift - 7p-7a.

I have two days before my first shift and my body isn't taking well to sleeping during the day Beyond the  normal concerns of being alert at the times I'm expected to be, I have other worries:

1. I am the father of two young children and I want to be able to be both adjusted to a night schedule AND be able to see my kids on my days off.

2. I have been out of shape my whole life and because of the academy I am finally fit. I notice that when I am more nocternal my eating habits are worse and that I'm less inclined and have less time to exercise.

How to adjust to this schedule, see my kids (and wife), and don't get fat again?

Any tips are appreciated.