If you turned down sex then you'd be playing your W's game. Why pretend you don't want it and add to your misery? If you turned down her advance she'd probably just be relieved and roll over and go to sleep and you'd accomplish nothing. These are the conclusions I came up with when thinking your exact thoughts, cause I've certainly had them. I've gone 3 months before without ititiating and my W didn't even notice.
A few months ago I took the day off on Valentines day, got all dressed up, picked my wife up from work (she had to work a half day) and then took her to the fancy mall in town. She didn't tell me I looked nice or anything but I noticed other women checking me out. It made me realize that my W low desire wasn't from me being unattractive (at least not to every woman!) and that somehow made me feel better.
The most important thing a father can do for his children is to love their mother.