Wat if gravity just stopped Working?

Ok. My Aunts managers 3 year old little boy is homeschooled and he is really really smart! He speaks spanish and other stuff, but anyways...The other day he was sittin on a barrel and he fell off and he said, "Mom if the earth is round then why don't we fall off?" and she told him because gravity holds us on. and he said, "Well what if gravity stops working, then what will we fall off and float off into space?" So they need to know how to answer his question in a way that he can understand. because he is worried that something will happen and gravity will stop working and he'll float off into space.