Thank you for your follow up.
Unfortunately, under the limited facts that you described, it would not be an entrapment for a police officer to conduct surveilance on a known drug location and then to pull over subjects suspected of purchasing / visiting a known drug location, especially if the vehicle your son was driving had some type of a license plate cover, that obstructed it, as that would provide the officer with a legitimate reason to conduct a traffic stop.
Also, if your son's wife voluntarily turned over marijuana and drug paraphenilia to the police officer, this evidence are more than likely will stand in court
against your son and his wife.
The criminal charge of possession of MJ <15g is a midemeanor and carries a penalty of up to 30 days in prison and find of up to $500.
Providing False Information to DPS is also a misdemeanor
and carries a penalty of up to 12 months in jail and a fine of up to $2,500.
These are pretty serious criminal charges and can result in jail time upon conviction, so I would suggest for your son and his wife not to communicate any further with this police officer or any other law enforcement agents and consult with a local experienced criminal defense attorney as soon as possible and to strictly adhere to their local criminal defense attorney's advice.
I wish you and your family the best of luck!