You want professional portraits of your large team, but there is no perfect day. You could do it Thurs, but 3 lawyers are in court. What about Tuesday of next week? No good. The CEO is meeting with a big client.
If you have a large team it's hard to find the *perfect* date. Schedule multiple days - either consecutive or once/month for 3 months. This also gives you a little room for retakes. If that first day was out-of-control humid, I promise your employees (and their frizzy hair) will thank you!