OMG, that sounds so frightening KatyK. I'm not surprised you have been left with a fear of dogs after your near miss. I've known some lovely, gentle Staffies, but sadly they became very popular with, shall we say, a 'certain type' of person, who bought them as a legal alternative to carrying weapons. Having a Staffie on a lead made them look hard, someone you wouldn't mess with, and of course, they probably treated the dogs badly to make them vicious. So now Staffies have this terrible label, and all of them get tarred with the same brush even though many of them make lovely pets.
But I would never, ever be happy about a Staffie being a pet in a family with small children, no matter what the responsible owners might say, simply because of their iron jaws. Not worth taking that risk.