3 months is definitely still in the normal puppy age of biting like crazy. So don't think you're doing anything wrong. Just be as consistent as you can with disengaging when bitten, and praising her when she bites her toys like she's supposed to. It can be tough with kids if they are not consistent with it like you are, and thus confusing the dog. But our pups I think stopped with the biting around 4-5 months

Ouch! Yeah that's very common. We have had two golden retriever puppies and they were very bitey. It was frustrating for quite a few weeks. But we stayed steady with the "Bite = no more interaction for a couple minutes" and eventually they learned.

Do your best to keep a toy between you and the puppy so she learns to bite it instead of you! Redirecting the biting to a toy helped us as well

New puppy? First puppy?

The puppy blues are real. If you have them, don't worry, they will pass. If the puppy bites, stop all play or engagement so they learn biting means no more fun