Weekend is my preference. A short poll covering date options, early evening versus weekend, in-person versus remote, and accessibility needs should give you enough information to approach venues. I’d avoid confirming a place until you know its capacity and whether any cost would need to be shared.
Is price per square metre intended for internal comparison, agent guidance or something shown to clients? Also, which area definition feeds it? A cross-country system may calculate perfectly while comparing different interpretations of floor area. I would keep the raw area, unit, currency and...