Time for the BYE BYE OUTSIDE program.
https://www.daycare.com/nannyde/the-...in-daycare.htm
Tell mom she and her son need to communicate BEFORE she drops him off so he can tell her his list of demands for the ride home. That way he can have cars, boxes of oreos, juice cups, pints of blueberries.... whatever ... in the car for him.
Have you read my book? The permissive parent chapter and Parental Attention Seeking Syndrome chapter should school you on the moms behavior.