I'm living in Oberhausen, which is just outside of your travel radius (36 minutes according to Google Maps).
I do not know yet if my friends and I will meet during your stay to play something, but I would gladly inform (and invite) you if something comes up. I added you as GeekBuddy, and maybe you could send me your travel schedule via PM? I'll also subscribe to this thread.
Don't hesitate to contact me!
Sounds great. I am pretty familiar with the area and Oberhausen isn't so far.