I am not saying that it is easy, or even sensible to require masks for two year olds, but on a recent flight, a mother was handed a mask for her one and a half year old who was acting out (not for her to wear, but because she kept on trying to take her mother's mask off) and she was happily putting it on and removing it for the rest of the flight. Maybe giving a mask to the child to play around with would help defuse the situation?