Do you want them to walk along the path as a Group with a distance between each entity?

In this case I would define one entity as leader who is the one who follows the path.
The other entities should not follow the path but follow one other entity.
a-> follows -> b -> follows -> c -> follows -> d -> follows path.

If you define a minium distance to the next entity, it is possible to avoid colliding.


[EDIT]
If the distance between these objects is too large, the following entities don't stay on the path.

hope this helps a bit