I've been very good about observing the Uposatha days this year, this year it falls on Christmas (US calendar). Any thoughts on observing while spending time with friends and family who are non Buddhist, or should I just just stay to myself?
You should be able to observe it without much difficulty. Everyone's family and friends are different, but at the same time there are many similarities. You should pause to reflect on how you will observe it, and consider reactions you might receive in advance so you can prepare kind responses (to keep everyone comfortable).
For most of the precepts observed on Uposatha, this shouldn't be a problem. Your friends and family likely won't be upset with you for not killing or stealing, for instance. :-)
Precepts five through eight could be a little tougher, depending on the people around you. But they're probably already used to you not drinking, so the fifth precept shouldn't be an issue.
The sixth precept might raise some eyebrows, especially if you're attending a party or family gathering where it might seem odd that you not share a meal with everyone. But you can explain it however you wish, from "I'm already full!" (if you really are; don't break the fourth precept!) to sharing your observance of Uposatha and what it means to you. You should do what feels right, and what makes you comfortable.
I hope you enjoy both your Christmas and Uposatha!