How do you react when he nips? He is moving into the 'teenage" phase of life, so he'll be testing his boundaries. When he bites, immediately pull your hands away and turn your back on him. Do not "reward" him with any kind of other reaction. Make sure the kids know this as well - he will learn that when he bites, all play stops, so it's just no fun.

Also, now would be a good time to enroll in a basic obedience class with him, it will teach him some and teach you some, and together you can help him become the dog he's meant to be! Boxers will always be bouncy and playful, but they are smart enough to learn rules and thrive with boundaries as well.

I would also skip the choke collar, that's not gonna help right now. okay?