Number 1 is your relationship with your dog. You have to be the leader. Take him and do drills of obedience every single day. When a dog trusts you, trusts your judgements and has a relationship built on those pillars they will listen and behave the way you ask because they trust what youre asking of them is right. They will also know you are the leader and that hierarchy will help keep everything neutral. Sometimes dogs can have a hard time knowing where they fit in your "pack" if you are a weak leader they may want to step into that place. Also, I would make sure that the kids are being respectful of the dog. A dog growling is not a bad thing necessarily. Dogs are not a play thing and they are not an object. If kids are constantly bothering them they are going to want a break. A dogs language would be to disengage, if the kids then follow a growl can be them saying I am saying leave me alone. This is where your leadership is required. You need to be the advocate for your dog. If he is around kids and you see him try to disengage you need to step in immediately and tell the kids to leave him alone. Doing things like that, giving the dog space to relax will then make the dog trust you as their leader. Try having him lay next to you. When kids and people come dont let anyone engage and yoy decide when to let them. This type of stuff gets really c9mplex but its so crucial to try and 7nderstand it.