Thanks for your response. I plan on speaking with my manager first.
Our system for determining holiday schedules involves a few factors. First, all staff sign up for the holidays they want off by ranking them (1 being their first choice, 2 being the second, etc.). Second, we look at what holidays the person had last year in the event there is a problem with giving someone their first choices. In other words, if you didn't get Christmas off last year and you want it this year, you're more likely to get it than someone who had it off last year. This system is well known by all the staff.
We currently have two unit secretaries who typically split the holidays. The other secretary worked Christmas last year and was wanting it off this year (she does not have children). I personally think this is fair and don't believe that holiday requests should be based upon the fact that someone has children and someone else doesn't.