Okay so you want a trusted dog to be a fellow protector of the family, and you want it to be good to your kids and visitors, also adorable at that. Thinking this you thought Golden Retrievers are popular medium size dogs with a pretty load bark, that it would be a great choice as a family pet. Well, you are right about most of those things, except the protector part.
I am not saying that Retrievers won’t protect you, if put in a situation where their owners are in danger rover will do everything he can to help you, maybe biting that intruder. But Golden Retrievers are not designed for guarding and/or attacking, they are dogs made to be an addition the family, with their playfulness for the kids and the kid in you, their loving nature for the companionship of everyone in the family, and their special retriever skills for assisting in hunts and assisting people with disabilities.
Don’t let that make you think that they are just actually large toy dogs though, they might not be able to stop that one guy trespassing on your lawn, but they are capable of far more amazing things. Like what you ask? Well, stopping terrorist and drug cartels of course! Yes they can be like Jack Bower-esque if they are given a chance to; Retrievers, with their keen sense of smell are used for checking packages and cargo for anomalies around the world. They are one of the preferred breeds for the job. So if you are asking if Golden retrievers are good guard dogs, you have to be clearer on what scope, because some of them guards National borders.
If you really want a guard dog and a family pet, you might have to choose one or get two dogs. Guard dogs have the nature of being one-man master; though their loyalty extends to your family their increased aggression pose a threat to young kids and to the ones who is not feeding him. Or better yet get a solid home security system and a lovable pet who will defend you during times of great danger, who knows somewhere in your Retriever’s genes might a little Boxer in him.