1) Always supervise interaction pit bulls and kids. NEVER leave a child alone with a dog. This goes for any dog. Even if it's a puppy. This is for both the child's and the dogs safety. If you read through articles of pit bull attacks online where children were hurt, maimed or worse, killed by a Pit Bull you will notice that in 99% of the cases they were left alone with the dog or dogs involved. This should be a rule rather than a tip. Use common sense and care. Small children especially should never be unsupervised around dogs.
2) Watch the children's behaviour. This tip is more for the dogs safety than the child's. Children can be brutal and even in the face of such harsh treatment, well bred, responsibly owned Pit Bulls are not prone to biting or "attacking" in defense. Make sure every child that plays with your dog understands how to behave around them. They should know to respect your dog and it's space and other things like toys, food, water, or their special bed.
3) Make sure all your dogs prized items are put away. Ah, nothing like a kid running around with a dried bully stick in their hands. lol. Not only is this nasty, your dog will want their bully stick back and attempt to get it. And in the process they could nip a finger or two. Put all your dogs favorite toys and treats away and where children can't get a hold of them to be on the safe side. To clarify, it wouldn't' be out of malice or viciousness the dog would get a finger or two. It would be by accident, an accident that can easily be avoided by putting such things away.
4) Start taking Obedience classes together as a family. If you're not already training your dog in basic obedience. Start as soon as possible. Having an obedient Pit Bull will help when kids are around. Not to mention adults as well. Teaching your dog to sit so they can be pet, laying down when things get a bit to rowdy, or to do a silly trick to lighten the tension of an over cautious parent is always a great idea.
5) Never Force your dog into a situation that makes them uncomfortable. Learn to read dog's body language. Some dogs simply get weird around certain people. Don't force the issue and make your dog say "hello" or play with someone they are showing signs of apprehension around. However, I have seen very few Pit Bulls get weird around people. Almost none now that I think about it. Since they are extremely people oriented it is quite rare to see them become skittish. However it does happen, so be aware of how your dog is reacting to people and if they do get weird, take them somewhere quiet they can hang out or continue on with your walk.