Well i guess no need to explain about bitcoins to teenager or children because when they see bitcoins at many place they will get interested in it that what is this? and the will themselves google it and starts learning about it. Like me i never learnt about bitcoin from anyone.
Every person is different in my opinion. Bitcoin telling myself to my brother, and he told what it was and he was not interested in knowing bitcoin. It would be very easy if someone is interested in bitcoin would be very easy to explain. But your will be very difficult if one is not interested because of how hard we explain if they are not interested we could not force him. The most important thing about bitcoin explain just what it is, if they are interested explain further.
Exactly we cannot force them to take part in bitcoin and its activities unless they wants to and they will only take interest in bitcoins when they see it occasionally and more often. After that they will ask 2nd person about bitcoins or maybe the will search about it on wiki or google.