Too easy to use crystal by accident

This game is fun and addictive! I have been trying to save up crystals to buy new characters. However, it was way too easy to click on crystals and use it to speed up tasks in errors when clicking fast. A large chuck of my crystals went missing after my kids played with it too.

Can you add something like a question or passwd to avoid using crystals in error!?

JJ more about Disney Magic Kingdoms, v1.1.0