My MiL gave my small an adult darts board one Christmas without consulting us, and I'm afraid I had the same reaction - as a mother of small children you are used to foreseeing the worst case scenario and trying to head it off. I don't understand your objection to children's scissors, but if that's the mother's wish you should abide by it. It only takes a second to have an accident with sharp scissors, and then how would you feel?
Water shortages and hosepipe bans
What do you think? I hate the plastic kids' scissors because I think they're a con and kids are perfectly capable of learning to use proper things if done safely.