Call 911 and take a picture of them.
Follow discretely and get a picture of license plate
Sounds shady
DO NOT call 911. That is not what 911 is for.
Call the local number. In some towns door to door folk have to register with the local police. They should know whether the person is legit.
I imagine on the Cape in early June, the cops are still looking for things to do. After Father’s Day, not so much.