I'm planning an event at your venue, and only advertising for one day I've got 30 people signed up, and 40 interested!
I need X, Y and Z resources available at your venue. And a large area of public space sectioned off for our use.
Can you advise dates where this is possible?
Subject: RE. Event
You haven't checked with us if you can run an event using our venue. We don't offer that kind of capacity.
We've never had resource X. We have about half the volume of resource Y you'd need. That's a bit disruptive.
Looking at the above, there are no possible dates.
Now engaging tactful mode to have a potentially complicated conversation, which will possibly upset someone well intentioned but overly hasty.