Reserved hotel rooms at Motel One Cologne Neumarkt (website).
The hotel is an 8 minute walk to the workshop venue.

Details of evening restaurants:

Wednesday 5th, 19:00
Brauhaus Reissdorf (German; a la carte)
Map

Thursday 6th, 19:00
Tanica (Italian; set menu)
Map

Friday 7th (for those still in town), 19:00
Udum (vegan; a la carte)
Map