Have it ever thought that it could be your Het Darwin is kinda frightened or uncomfortable on you?
Snakes are natures seismographs and because of your body temperature, minute muscle contractions, blood flow or skin sweat.... your pet Het would rather forget your company until it gets used to all those "environmental" factors.
Kids (assuming your son is a minor) don't have as much "environmental signature" as an adult.
You could wash your hands, body, arms etc several times but they'd still "acquire" how you were yesterday.