It's that time of year where your employees have either planned for time off, or at the last minute will make an impromptu request like "My family is coming to town for three days and I'd love to spend time with them." There are several ways to manage these requests and still maintain work flow processes.
First, be sure that you have a written policy that has been shared with all staff members stating how vacation and/or time-off requests will be handled. It's very important that the policy states what the consequences are for noncompliance. For example, if Joe asked for time off three months ago and Mary just asked for time off last week, it's important to explain to Mary that your policy requires at least 30-days in advance for time-off requests, and that all practice tasks must be covered in order for an employee to be absent.
It is also very important that all practice staff know how to perform the basic functions of every job associated with their work station. They do not have to know all of the subtle details, just enough to get through an employee's absence or vacation. So, when Joe is ready to leave for his vacation, you will have staff members who can cover his workload. This additional work can create opportunities for overtime, so be sure you have a solid policy in place that requires a supervisor's prior approval for all overtime. You can also "bonus" people who stay to work over the holidays, so that there is no change in employee morale and job satisfaction.
The biggest area of potential conflict is if there is more than one person approving time off for staff. If communication between senior staff is not prompt and clear, this can become very detrimental to any practice. One way to handle this is if a supervisor verbally approved time off for an employee, but did not follow the practice's written policy, do not allow the employee the time off.
There have been scenarios where non-approved time off has resulted in employees calling in "sick," during what would have been their requested vacation time. I believe you can still request a note from an employee's physician upon her return. This should be clearly written and explained in the practice's sick-time policy to deter this from occurring.
In the event that all but a few staff members are left in the office over the holidays, for whatever reason, consider consolidating the work week, if possible. Staff could work half days, or you could close the practice for the whole week, if emergency coverage is available. If you find yourself with a small group of loyal employees, try to do something special like throwing a small office party, to let them know they are appreciated for working through the holidays.