Interesting gathering.....I see there's the American Retro Bar & Grill on 11th Ave / 51st St that has space for parties/events......I have not been there, but could do some recognizance if needed.......
To make you feel at home, we also have a German place, Hallo Berlin, with a small outdoor area on 10th Ave / 44th St.....and many bars/restaurants on 9th Ave....I guess it depends the size of the crowd you draw and if Rammstein is opening for you