OK. I talked to CJD and Muellestumpe.
Good news is we could do the barbecue with wild boar on a spit at Muellestumpe.
Bad news are much more:
1) Muellestumpe has only 7 bedrooms and two appartements and these are already booked for Saturday and Sunday. So if someone would stay there he/she would have to checkout on Saturday morning
2) CJD says we might habe a chance for Photokina 18, weekends in September and October are often sold 2 to 3 years in advance
What will I do now?
Search for other places, quite possible one that is still near Photokina, can accomodate 20 to 40 Nikongearheads, allows for Wild Boar Grilling etc.
I will call some people I know in the accomodation business... CU