I am at the splash park. Just ahead of me is a mum on a bench. Her son is repeatedly filling a water bottle and throwing it in her face. She is very meekly telling him no. He is paying no attention and teaching his little sister to do the same. It looks really quite aggressive. I would say he is about 9, but big for his age. Do I intervene? I would never normally intervene is someone's parenting unless I saw a child getting hurt. I offered her a towel which she accepted.