Actually bitcoin can be expressed to children by some special techniques.Such as you can first inform them that bitcoin is like your own country's currency..it is an global currency like dollar, taka, euro etc..And you can tell them that they can buy chocolate, dress by bitcoin..i fell it's a smart way.

i would like to give you a positive answer..yes, you can do without investment. You can complete many free offer
in bitcointalk and join in singnature campaign. beside you can earn special skills like seo, programming, web design. gradually you will be able to earn a lot..Remember "the more you learn, the more you earn" first invest time..not money.