If there is an exchange there in your country that allows to convert your bitcoin to fiat in less than an hour. its probably not a good idea if one of them is a huge spender or worse
if he has a habit of spending his savings even though he's only halfway done lol. if we're talking about the other one, then its better to save in bitcoin as the price increases.
the main problem is where will they get the bitcoin? and no, mining is not the only way to earn bitcoin. mining is a complicated process you'll need a lot of things and it costs a
lot, much better for you to search it on the web. You can also search for the ways of earning/saving btc that are suited for your cousins but my suggestion is to either work for it
or buy it bit by bit
Sure, it will. I will teach my kids how to use BTC and they will know how to save and spend BTC or any other coins.