my ex-helper has 4 kids herself. she has experience in dealing with kids, but (1) she lacks knowledge with modern child-care e.g. don't know how to use bottle boiler and (2) lazy (e.g. don't want kid to play on mat or she will have to clean it afterwards, allow baby to drink milk while sleeping which is very dangerous)
So I mean, whether the helper can be helpful to the employer not only depends on her background/ experience but also her character!
Just cos I have a kid does not mean I have to be good to yours. In fact, when comparison is made, she will be sad as her kids don't have the opportunities and wealth your kids have.