I think the simplest and easy trick for a 7-year-old child would be spoon-bending trick. Here is the description: The key to performing easy magic tricks for kids like this is all in how you hold the spoon while “bending” it. Grab the spoon and hold it with both hands closed around the handle. Make sure that the spoon is not peeking out the top of your hands. Now place the bottom bowl of the spoon, open side up, onto the table. As you begin to press down on the spoon, you allow the handle to slide along the inside of your hand until it reaches the bottom of your palm. This makes it look like the spoon is bending from the spectator’s point of view, even though you are not bending it at all. Your other hand that appears to be gripping the spoon is hiding the spoon handle sliding in your first hand.