Bonnie, I's sorry to have missed your message before now.
I don't have any Mittelstaedt info for you, but I can tell you about Henrietta SCHUKAR of Town Theresa, Dodge co., Wisconsin, one of the godparents of your twins. She was Henrietta Grawunder, born in Bernickow, Kr. Koenigsberg Neumark, Brandenburg. She and her husband Peter Schukar, and 3 children came to the US in 1852. The WURL name also appears in church records in Bernickow.
Have you looked at FamilySearch.org? The church books from Bernickow have been extracted so you can see the actual transcribed records. There will also be more info if you can look at microfilms of the records, available from familysearch.org.
I'm not finding a Wurl-Mittelstadt marriage in those Bernickow records at familysearch.org, but both of those surnames do appear in marriage and baptism records there, as does GROSSKOPF.
Perhaps by now you've found the information you were looking for. If not, I hope this is at least a little bit helpful