Galileo is usually credited with first describing the idea that objects will fall to the Earth at the same rate, regardless of mass (there’s some debate over whether he actually experimented with this at the Tower of Pisa though).  So yes, a feather should fall at the same rate as a bowling ball…but air resistance gets in the way of performing this experiment.  Unless you remove the air of course, which is exactly what physicist Brian Cox did in the video below, using an enormous vacuum chamber in Ohio.  Great video to show your kids!