It was at the beginning of their dating relationship, it should STAY there. When I first started to date my husband, I wasn't at all "in" to him. But a few years of dating and 35 years of marriage later, I'm glad he can't find out what my thoughts were when we first started dating! Geez, not everyone falls in love at first site, but that does NOT rule out long lasting love! As for his opinion on children, most young single men don't WANT to find a woman who has children. A friend of mine had a house full of cats, you'd be hard pressed to find a man looking for a woman with a house full of cats! But once the men fall for her, they fall for that extension of her as well, her love for her cats. Otherwise, they definitely would not stick around nor propose. Same with children.
As for whether or not her husband slept with another woman when he first began dating his wife, how is that a problem now? How is that infidelity? He wasn't in an exclusive relationship with either woman. He didn't say that he went to the woman's place, just posted that he intended to go. So what? He obviously fell for the woman to whom he is now married, he is happy, she is happy, but if she harbors this hurt, there could be a problem. He can't change the past, he has done NOTHING to reflect that he is anything other than a loving, doting husband/father, and she needs to let this go. Her ego is hurt because he posted this and strangers read it. She needs to laugh about it and tell her husband he ought to post a retraction -- dated years later, for those posts! It should be done tongue-in-cheek, but nonetheless, it will help her to feel better.