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? 
You could do that since 0.01 btc is quite affordable right now. So if something happens, you wouldn't losing much to be honest. But do keep in mind that you will need to securely create that wallet and make sure nothing damages the paper wallet. Better to make some other sorts of backup just in case. And if everything goes fine, i guess the 0.01 btc will worth a lot in 15 years.