If a teenager understands that a bank keeps track of every payment and movement of money, they can understand bitcoin. Bitcoin takes the responsibility away from the banks to keep track of the ledger (removes the middle man), so that people can transfer money directly between each other 
Your idea is much confusing and children would not get interested with bitcoin. Just a simple explanation like, do you want to have a bike? We can buy you one because of bitcoin. Then just let them explore and say something or explain if they ask questions. Just tell them that bitcoin equals money.