I know you don't allow users to change primary keys but permit me to ask this question.

 Let's say I have a theoretical table of recipies like

RecipeID         int    PK  (Identity Column)
RecipeName    varchar(35)

and a directions table, which tells a user what to do and the order in which to do it.

RecipeID         int    PK (From Parent)
Order              int    PK
Activity            varchar(250)

In the child table the combination of RecipeID and Order makes a very logical key field but the Order may need to change if the user wants to add a new step.  Of course the user could change the Order field to an existing value and create a duplicate but they could not save the record in that state. So are you saying you would create the table like this?

RecipeID         int    PK
DirectionId      int   PK  (Identity Column)
Order              int
Activity            varchar(250)

This seems like a waste of a field. SQL management tools have always allowed you to change primary keys and they have those cascase update rules as well.

You do not have change the Directions table. You could add a new record with the new Order value, copy over the other fields, mark the original as deleted, and save. If you are working with a collection, then collection.Save() is sufficient. If you are working with two entities, then I would save both inside an esTransactionScope.

This is the same approach as would be taken for a ManyToMany associative table with a composite key. You Associate the new entity and Dissociate the original. EntitySpaces does an AddNew and MarkAsDeleted, respectively, behind the scenes.

I would change the definition of the 'directions' child table (if it's under your control) to the following:

Recipe Table:
RecipeID         int    PK  (Identity Column)
RecipeName    varchar(35)

Direction Table:
DirectionID      int    PK (Identity Column, autonumber)
RecipeID         int    FK (From Parent)
Order              int    (just a property)
Activity            varchar(250)

By changing the Order column to just a property, a simple ES entity will allow you to save order changes without impacting any key(s).

(2 cents...)