Take the cards out of your deck of cards... Let someone exam and shuffle them. Now YOU replace them in the box. Take a card, face down, out of the box while telling them what the card is. Now reveal the card to show them you are right. They will be amazed at this feat of mentalism and ask you how you did this kids card magic trick.
With the hole facing you, hold the deck of cards up right, this will allow you to take a peek at the cards through the hole in the box. nonchalantly turn the box downward so that the back of the cards are facing up ( Make sure you hold the box so they can' not see the hole ). Pull out the card you just peeked at with the back facing everyone. Think a second and tell your friend the card you just pulled out and show them the card to confirm it. You will need to turn the box back to you in order to see the cards every time you want to think of the next card in the box.
Kids let a grown up do this for you. Using a box cutter or scissor, make a hole in bottom corner just big enough to see the index of the card; As seen in the picture above. Put the cards back in the deck with the face side facing the hole in the box.
You need to always keep the hole covered with your thumb or hand, whichever feels more comfortable to you. Practice the moves of this card trick, until it feels natural to do. Make up a fun story or patter to amuse and wow your friends and family with. The patter and moves will help hide the fact that you are peeking at the cards.
Hope you enjoy this and the many other magic tricks for kids we have for you.