Why don't you order the church records for Schwinkendorf from the LDS and see how the name was originally spelled in the baptismal records? Once you see the family names, it should be apparent.
Here is the link for the church records on microfilm available through the LDS:https://familysearch.org/search/catalog/248739?availability=...
And here are the records for Grubenhagen:https://familysearch.org/search/catalog/248158?availability=...
The family's original spelling probably varied between
two forms: Sade(n)wasser and Sade(n)water. From the following gen forum in German, you see the name Sadenwater
appears in Schwinkendorf.http://forum.ahnenforschung.net/archive/index.php/t-30746.ht...
Good Luck and hope you find something in Schwinkendorf or
perhaps you will want to e-mail some of the people in that forum.
Since you did not post any info on when they emigrated or the names of the children, I did not look for them in the passenger lists.