Re: I'm just thinking about to give away to my 4-year-old nephew a 0.01 BTC
That's the max that I can afford at the moment (I'm 22) but I want to save it on a wllet of paper and give it to my sister telling her to keep it safe and that we will give it to him when he is 18 years old. Do you think is a nice idea? 
This is great and meaningful when you decide to donate 0.01BTC as an item too. If you write in a private key, I suggest you put the paper in a glass jar and bury it in the ground with your child. And say we will exchange it when he's 18th birthday.