With your kids, you really shouldn't. It is all in how the pitbull was raised. If treated well from the start of life, a pitbull can be a great family dog. However they are known for agression, and like you said, you have no idea how her previous owner(s) treated her. She might be a fine dog for your family, but if she was abused in any way there is a high chance she will become defensive. When your child is feeding her, for instance, and is too close to her food dish, she will bite. (Happened to me when I was 9) It is common they have food agression, and are protective of their owners. Because of this, you or your family may not be bitten, but a stranger will be. Pitbulls have all sorts of issues with children, other dogs, cats, meeting strangers, even people with deep voices can frighten them and cause them to spaz out, often injuring people. Pittbulls are just not exactly family dogs (in most cases) and adopting this girl will definitely be taking a risk. Is there a way you can get in closer contact with the dog? Bring your kids in and introduce her to them? Maybe walk her? Make sure you ask the shelter for any information you can get on her. It is up to you.
Because of the history of agression in pittbulls, at my local shelter it is illegal to adopt a pittbull if you have children under 12 in the house. They generally just aren't good with kids. But remember that every dog is different and you should still give her a chance. Just make sure you get to know her better, and your kids do too before making your final decision.
Good luck (:
My mom had a pitbull mix when we were growing up...