I see where your coming from and its great you've identified issues and spoke about them with eachother, it sounds like you could use a bit of extra help, maybe some relationship counselling could be of great benefit to you both?
I can totally empathise with your wife. I am a nurse too. I am only 22, yet I am absolutley shattered all the time, and rarely feel lke having sex. I have just moved in with my partner who I love very much, but I feel for him because my job is so stressful I tend to come home in a bad mood most days (no matter how hard I try not to). Please understand it's very difficult for your wife not to bring her work home with her, we deal with some harrowing cases every day, combine this with all manner of shifts and its enough to kill any sex drive. It must be much harder for you both than I can imagine, as I have no kids yet. Sounds like you both have very busy stressful lives and it can be hard to take time out for eachother sometimes.
You don't say how old your kids are, but that can be another factor. It may be that your wife has lost her libido after having her children, which is incredibly common. There is lots that can be done about this, if your wife is willing.
I know its hard, but please be patient with her. You don't say what job you do but frankly with you both working shifts and her being a nurse, plus you having kids, I'm not surprised your love life is 'slow'. As long as you can both establish you still love eachother and want to work it out, you have the foundations to start getting back on track.
Its hard with shifts and kids, but try to set aside an evening every week or every fortnight to start, where you get a babysitter and spend time alone just the two of you. This is your time to reconnect, you can do what you like. A romantic meal is always good, as is a night in with the house to yourselves, think candles, wine and soft music, i'm sure your wife would appreciate a nice back massage (I know after a long day on the ward i'm very grateful when my partner does this - and it can often lead to other things! But don't expect it, or even hint at sex, it might make her feel pressured even though you don't mean it. Let her come to you).
It might feel like your getting nowhere at first, but its so important to just give her plenty of kisses and cuddles and make her feel relaxed. Once you've got the closeness back (without sex) the rest will follow. Please consider counselling, it could really help. From your post, it sounds like the classic stuck in a rut situation that comes to everyone rather than the end of a relationship. Let us know how you get on.