Your husband needs to get into the habit of initiating sex with you, and you need to train him how to do it in a way that will predictably arouse you. One problem you seem to have is that he assumes that you will do the initiating. When you don't initiate sex, he feels rejected. I strongly recommend that you make it very clear to him that he will be initiating sex for the next three months, and that he do it with the purpose of learning how to make sexual arousal almost effortless for you. Both of you should experiment with various approaches to getting you sexually aroused after the kids are in bed.
Women do initiate sex sometimes, it's true.
But the most common experience is for the man to do most of the initiating. And he has the unenviable job of having to learn how to do it right. Men don't like rejection any more than women, and after a man fails to arouse a woman, he gets gun-shy. That may be why your husband wants you to do the initiating, because if you initiate sex, he knows he won't be rejected. And your failure to be aroused may be interpreted by him as rejection.