I showed and bred Champion Golden Retrievers for many years so I will chime in with that experience and those of my mentors that have been showing and breeding for over 40 years.
Goldendoodles are a mixed breed between a Golden Retriever and a Poodle. Both breeds are very active and energetic. They were also both bred to retrieve game which means they are MOUTHY. Goldens especially like things in their mouth and they don't discriminate, hands, socks, pants, feet, shoes etc. They need to be taught early on not to put their mouth on skin. They learn part of this from being with their litter mates. I am guessing you got this pup prior to 8 weeks of age. The rest they learn from their pack at home. You are supposed to be the pack leader. This puppy does not see you as such and is treating you like a littermate.
Forelegs down and butt in the air is an invitation to play. Not a display of aggression. Often times what you hear
as "growling" is simply "talking" there is a difference. Many Goldens and other breeds and mutts can be quite vocal when excited and happy so talk when they are very excited. Sometimes it's with a toy in their mouth and sometimes not. Many dogs, including Goldens "smile". They peel their lips back and grin at you, mostly front teeth showing. It will help when you understand canine body language. You will understand what you dog is telling you. It easier to communicate that way with them using their own language. Remember they don't speak English. Mother Knows Best is a wonderful book to help with training and communication with your dog. All of the families that where approved to have one of my puppies were required to purchase this book and read it BEFORE they got their puppy. Reputable breeders spend a LOT of time with the new families before the pup goes home and are available 24/7 for those families for the life of the dog.
I also showed Cavaliers. They were bred to be lap dogs. While they can be quite sporting they are not mouthy as a rule. My 9 year old Cavalier does like to carry around toys but she was brought up around a bunch of Goldens and just did what they did. I don't think she realizes she is not a Golden
Please educate yourself on canine body language and begin training this puppy now. Make her understand that you and her two legged family are the pack leaders, not her. She can read your body language and your son's and she thinks you are all on the same level. If she were of my breeding I would be recommending you tether her to you at all times. She does not enter a door/entry way before you. She does not eat until she does something for it. "Sit" is easy enough to start. Start training her. Do not train a baby like her for more than a minute or two at a time though, she will lose interest.
If you hire a trainer to help you please be careful. People can get certified in dog training online without ever having gone near a dog. If you can find someone who does competition obedience, that will be a good bet. All of my puppy's families were required to go through
group obedience classes with my grandpuppies. I don't recommend private in house training. Your puppy needs to learn to obey you in ALL situations not just at home. The best places to train are where there are other dogs, puppies, people, sights, smells and surroundings that are FAR more interesting than "mom or dad". When they learn in THAT type of environment they are more likely to obey when it really matters like slipping the leash and heading straight into traffic.
Hope this helps.