Ya, family holidays are stressful. If you smoke weed and know a relative smokes weed, it’s tradition to “go for a walk” or have a “safety meeting” or “take out the trash” to break away from the main group and get some fresh air.
In my family it’s my brother and his wife. Usually right after dinner.
If you’re pounding one out that won’t really save you. He probably games with headphones and just doesn’t want to get jump scares by mom.
I always had a desk and a bed and I made a point to never have my back towards the door when I was at my desk for the above reason.