At her age, it's most likely play and not aggression. 3 months is young to see aggression and so many lab puppies do this. Lab puppies can be very mouthy and energetic. My older puppy did the same thing, along with then racing around like he had lost his mind in an excess of excitement and energy. I had holes in my sleeves and my kids lost a couple pairs of yoga pants to his jumping and nipping. I learned to turn away from him as he was coming toward me so that he couldn't actually make contact, then I encouraged him to run around to get some of that energy out. He did this every day as a puppy, but he grew into a big loveable moosh. Labs are such popular dogs, I think a lot of people aren't expecting or prepared for their wild energy as puppies.
Sometimes they get in to this crazy jumping barking mode when they're overtired as well. If it seems to be happening at a certain time of day, like later in the afternoon when she's been awake and playing for a bit, sometimes you can head it off by letting her go into her crate for a nap.
If she's jumping and barking at the kids, help them learn to turn their back to her, fold their arms, and refuse to engage. It can be scary for a kid to have their wild puppy jumping at them but if they can learn to turn away so the puppy cannot "get" them, it can help. Rather than try to run after her to get hold of her when she's like this, keep a short leash on her that you can grab or step on as she races by.
By the way, my younger pup had her older brother to jump on and bite at, so she didn't do it to us as much as her only puppy older brother had. She wasn't a better or nicer puppy, she just had another target for her energy and we had to protect our older guy from her energy sometimes.
It will get better. Take her to puppy obedience classes, be consistent in training, and know this will pass.