mongoDB design - to embed or not to embed
I think I found my answer from the mongoDB manual: 

In general, use embedded data models when:


you have “contains” relationships between entities. See Model One-to-One Relationships with Embedded Documents.
you have one-to-many relationships between entities. In these relationships the “many” or child documents always appear with or are viewed in the context of the “one” or parent documents. See Model One-to-Many Relationships with Embedded Documents.


http://docs.mongodb.org/manual/core/data-model-design/

The later scenario would apply to me.