My name is Martin Pytr, I am a full tim genealogical researcher from Czech Republic.
To locate the Seitendorf is necessery to know whether the village belonged in 1882 to Prussian Silesia or to Austrian Silesia.
Area of Prussian Silesia is located in Poland tody, so called Austrian Silesia is located mostly in the Czech Republic now.
In the case that the family came from Austrian Silesia, I can help you. In Czech Republic are several villages what waere in 1880s called by the German name Seitendorf. Most of them are located in Bohemia and Moravia but one is located in Silesia, today is the village called "Horni Zivotice" in Czech.
In 1880s the village belonged to "Bezirk" (district, county) Freudenthal (Bruntál).
If you wish I can check church vital registers of Horni Zivotice, for you.
If you are interesting about it, send me e-mail, please.
Martin Pytr, Czech Rep.