This thread brings back memories of my child hood.
Your hunch is right. The cars of senior officers did have distinctive stickers on them. Soldiers walking on base were required to salute the car when it passed by- even if the officer was not likely to actually be in the car. I cant remember if all senior officers above a certain rank were given the stickers, or just those in command positions.
In regards to stickered cars and dependents and gate inspections.....
My father was an officer with a stickered car. As you suspected, inspections of my family at gates were token. Stickered cars also had some other neat privelages such as being directed to priority / reserved parking at base events- even if my father was not in the car. We were also allowed to pass though convoys of military trucks while other cars were held up.
Anyways....
Based on my gate experiences, I can see a stickered car being driven by a respectful and sober dependent being given a token inspection unless there were very high red flags. Injuries might not be noticed. And if noticed, the gate guard maybe inclined to accept "Ohh, I cut my hand helping replace a glass window at my GF's house- Yes, I"ll get it looked at." explanation with out referring the driver to the senior NCO on duty and logging the incident.