Is it possible to have an updateable log for an event?
What about using activities and a contact for the shelter?
Each activity would be an entry, you can use activity types, so it might make it easier to get some analysis on the log.

There isn't any direct link between the log and the event, but you can filter by date and get the activities linked to a specific event (night). 

you could write an extension to change the layout of the event backoffice and provide a filtered view.