In my experience Gwinnett cops are quick to be a$$hols about this kind of stuff, especially with kiddies. You should have been cited for your expired tag and sent on your merry way. If they were really concerned about your insurance they would ask you about it and give you a chance to provide the info. Cops nowdays are 'military trained' and most have been largely voided of any common sense in terms of talking to and dealing with human beings.

My wife was stopped for speeding. I had attached a tag to her car that didnt even belong on that car, but another car we owned. The cop (not Gwinnett) was very cool about it and actually talked to her like a human, allowed her to verify with him that there WAS insurance on the car. He only warned her for speeding but cited her for improper tag and told her just to take care of it and provide proof that it was and that there would be no big deal. Unfortunately some cops dont have the common sense to just talk to people a little and do the sensible thing.