Is this game safe or is it too dangerous?

Yes, this is too dangerous. In a perfect world, this would be a silly overnight adventure. But we don't live in a perfect world. And so we always have to plan for a NOT perfect world. How about if somebody found out your folks were away overnight and decided to take this time to rob your house? Bad enough if you are safely locked in the house and near a phone to call the police. But outside, locked to a tree? How about if one of you gets sick or passes out, especially from standing hugging a tree for hours and hours? Or it rains, with lightning? Do you get any animals where you live, like racoons or opposums? Or skunks? What if one of them comes by and decides to attack? They do, you know. What about mosquitoes? Spiders? Ants? Going to the bathroom? Shall I stop now?