My girlfriend and cousin both dated, even though they were single moms, and found wonderful new husbands to help them raise their children. These are responsible, loving, and intelligent women who made fair choices their first time around - took a few years, examined the failings of their first marriages - and then looked at the dating scene with totally different eyes. They chose very wisely this time.
I agree that children do better in two-parent households, presuming that the single parent is smart enough to choose wisely, act responsibly, and put the children's interests on equal standing with their own when it comes to dating/selecting a new spouse.
But can we both agree that women who chose unwisely not only risk themselves but their children? Women who will ignore abuses against their children to hang onto a boyfriend would be better off not dating at all. Further, women who leap from relationship to relationship (or from marriage to marriage), who have a revolving door of lovers coming into and out of the house, also are putting their children at risk. Even if the children are never physically or sexually abused, the children may form attachments only to have those ties severed repeatedly, leaving them confused and wounded.
Heck, this doesn't just apply to single women, this should apply to all women and men - period. It always alarmed me that friends would sometimes hang onto toads, thinking that a kiss at the altar would turn them into Prince/Princess Charming.
God bless you for opening your heart to your wife's children, and making them your own. I'm sure that they are better people for it.
We could, however I think the threat is overrated. Most men, I believe are suitable fathers. I'm certain that more children suffer from the lack of a father, than suffer from a bad one. Stepfathers included.