The cycle accessory system for child strollers can convert an ordinary child stroller into a multi-child transport unit. The multi-child transport unit can have at least four modes. The first mode (referred to herein as the "child control" mode) allows the lead child to power and steer the multi-child transport unit. (Note: even in child control mode, an adult has the ability to at least keep the multi-child transport unit stationary.) The second mode (referred to herein as the "adult control" mode) removes the ability of the lead child to power or steer the multi-child transport unit and returns control to an adult to power and steer the multi-child transport unit. The third mode is a multi-child transport unit storage mode. And the fourth mode is a tricycle mode.