When taking care of a minor with permission of the parents, what is the legal force of any rules the parents set?
For example, if I look after someone's child, and they tell me the child may not climb trees, or may not drink alcohol or may not see a specific friend, and I allow or do this nonetheless, what are the legal consequences?
Would that be a crime? Or only a civil wrong? Would it depend on whether the child actually suffers harm as a consequence? Would it depend whether I personally violate the rules (e.g. by personally handing over alcohol), or if I just tolerate something?
I am particularly interested in answers about Germany, but other jurisdictions are welcome.
This was inspired by the question What are the drinking age laws in Germany?