I don't actually know the local situation, what is "Grunbach Nord"? 

If you know the administrative boundary, then yes I would suggest to use a second area/relation for that, because the residential area doesn't include the school, church and graveyard and the commercial area Breitwiesen, but presumably they are part of the administrative area.

Alternatively a single node in the center - maybe "place=suburb" or "place=neighbourhood" - if you don't know the exact boundary.