Sorry you have to experience this at family gatherings. Geee sure puts a damper on just having a good time.
What I did with my neices and nephews was....I made sure that mom and dad were no where in sight, and gave them each my business card. Told them to put it away in their pockets, put it someplace no one knows, and if they every need anything...call me I will be there. Seems to have worked. They call me when they are in a jam since my JW family only wants them to feel bad about being a kid. So far nothing harmful, I did tell them if they did anything against the law, or was harmful to themselves or others I would have to tell their parents.
Hate you have to do that with family that shun you.
Leslie