I had 2 female staffies and they were the most adorable, loyal and affectionate dogs I ever had. They also attended kennel club staffy training so that they were brought up properly. They adore children and are very protective towards them however like any dog you wouldnt leave them unattended with small kids. The older of the 2 absolutely hated strange dogs though so she had to be properly controlled outside and never off her lead. I also found that my girls were ALWAYS attacked first and eventually they'd retaliate and when staffs give warnings they sound fierce so they'd get the blame when they hadn't even started it!
One time one of my girls was on her lead and attacked by a loose dog and the owner had a fit on me to "control my dog" which was STILL on the lead. To say I gave them a mouthful was an understatement!
Would highly recommend the breed so long as you are serious and have the time to spare as they are very demanding for attention. Never buy from a chav either as the pups take on the early socialisation from the mother and if they're not properly trained or have been used purely to breed then you'll have a problem pup.
Always ask for a diet sheet and SEE the mother, preferably the father too, look at how they live, are the dogs kept outside when you intend on having the dog live in the house etc etc?
They also need tons of exercise so with a new baby dont bother as they'll get destructive and chew everything if not walked enough. Wait till the kids are older