One way of doing it would be to apply the path to each of the objects, and then adjust the Path Offset parameter of each object to get them arranged in the starting positions that you want. Then simply animate the offsets to make them travel along the path.
If you had Motion 4 you could probably use the Link behaviour to make the movement of one object drive the movement of all the others.
Another way would be to get one object following the path, and then simply duplicate it and stagger the duplicates along the timeline. That would work particularly well if you wanted the objects to pop onto the screen one at a time rather than all be visible from the start of the animation.