Well that is terrifying, the fact you have to think ahead like that, fearing what you might have to say, assuming a default. Since it is a binary option with m

Well that is terrifying, the fact you have to think ahead like that, fearing what you might have to say, assuming a default. Since it is a binary option with moral overtones and since your boy will eventually compare notes with his contemporaries you could gift him a story that sidesteps the matter. The story might not be grounded in truth any more than Santa Claus is. The mythical backstory could be that it was decided on a coin toss, heads it stayed on, tails it came off. Maybe embellish it so that the doctor, his mum and yourself all had coins, it being a 'best of three' with the doctor calling 'tails', you calling 'heads' and his mum having the deciding coin. Such a white lie can be useful for him when he needs to dig himself out of a conversational hole when he gets older so as to not have that awkward moment with a religious workmate/sister's boyfriend etc., even if by then he knows the story is a myth.