Scheduling staff members

I run a service based business in sport - I have 3 staff albeit not full time. 

How can i best set up the calendar to show availability across all three staff members for the same service?

E.g. I'm going away for 3 weeks and have it blocked off in my calendar however my two staff members will be around, however will still have other commitments. How can I make the calendar show availability to customers for when my staff have free time in their calendars?

1. Do your staff have access to the calendar to update it weekly? they could all download the acuity scheduling app ( scheduler for squarespace) its the same password and login for your squarespace site, and they will be able to change it right from their phones, you can set it all up before you go and make sure everyone knows how to work it 👌 

They can do - Would this also work if they synced their own calendars?

And then on a more permanent basis, how could I set it up so that it will show availability from all our own synced calendars?

E.g. I'm unavailable but one staff member is free, for it show availability to customers?

Without them having to manage an extra calendar other than their own they currently use (office365/gmail etc)