How does your wife feel?
Does she feel attractive?
does she feel loved?
Does she feel wanted?
Does she feel sexy?
We all need to feel hot and sexy when it comes to the business between the sheets.
Your DC are very young too, you both work. How do you both find the time for sex?
I feel you need some adult time, from the sound of it babysitters won't exist (maybe they do so take advantage)
One way or another, it seems to work for you normally with no sex involved so go out (or stay in) once a month.
Go to the movies, rent a DVD, go out for dinner, cook a meal.
Start dating, woo her, chat her up, flatter her, tease her, have a nice photo (or mildly sexy one) as the screen saver on your phone, let her know you fancy the socks off of her.
But don't expect hot steamy sex and be satisfied with a kiss and cuddle in bed.
Why pile in there with an ultimatum saying she has broken her vows etc etc etc. That's not going to make her feel any better of herself.
Maybe you have tried this, but nothing will change all by itsself.
Tell her that's what your going to do, tell her your going to make her feel special, hot, sexy.
but your DW will need to make an effort too, she will need to accept gracefully your compliments, she will need to accept that your being like this not just because you want sex but because you DO finder her hot and sexy.
Make her feel hot and sexy and the sex will come naturally