Along with what everyone else said, you need to teach your children not to run, scream or play chase with the dog because that's what set her off. This can be difficult because it's often children's first method of playing with the dog. I recommend getting a trainer or going to a class with this dog ASAP. The children should be included in this, or have the trainer talk to them about how to properly play with their new friend. There are also books for kids on dog training and how to interact with dogs. Right now you should be very careful and not allow the kids to interact with the dog without supervision.
Since you bought this dog at a pet store it's also likely she has poor bite inhibition (control over how hard or soft she bites) because the pups learn that from their mom and siblings, and they are typically separated them way too early to be shipped to the stores. I see as well that you were/are having housebreaking issues. Dogs born in puppy mills (hellish places where all pet store puppies come from) are known to be notoriously difficult to housebreak. This is because they are kept in small cages in the mills and stores, so they learn that it's acceptable to relieve themselves wherever they are, including where they sleep and eat, which most dogs are adverse to. This becomes a much harder habit to break the older the dog gets. I DO recommend crate training, but with a dog that has had experiences like this, she might just go in there too. However, it's worth a shot. If you're adverse to that I would section off the kitchen or other small room while you're housebreaking. I see you said the dog is destructive as well. She's still young, and Labs are high energy dogs. I would suggest you make sure she gets lots of walks and romps, and some nice chew toys like nylabones and Kongs you can stuff treats in, which will also occupy her mind if she's bored.
Best of luck with your new dog and I hope we can help you along with this!
