You ever notice how the kids' powers kind of match their personalities? That and their names? Violet likes to keep to herself and puts up shields around herself. She also creates violet-colored force fields. Dash, being the typical little kid seems to be on a constant sugar rush most times. He also has super speed which helps him dash all over the place. As for Jack-Jack, being a baby means he's got any kind of personality to suit his mood and the situation. His powers also reflect that he's a sort of Jack-of-all-trades.