As someone who spent years as a single adult in a small family, I will say it can be depressing to have that small family not gather for the holidays - it's not like you have a family of your own to share it with. And, while there are friends who will usually be happy to invite you to share their holidays, it can be awkward and uncomfortable as a bystander to someone else's family gathering.
So, having said that, I recommend being honest with the "kids". Simply tell them that you'd like to head south earlier this year, but that would mean you'll miss Christmas with them.
You'll likely one or more of the following responses:
1. That's great! I was thinking of going to xxxx, but didn't want to disappoint you.
2. I wish you could be here with us, but you deserve to do what you want. Go and have fun.
3. What am I supposed to do? Just sit in my apartment all alone? How could you be so selfish!?!?!?
4. That's fine. I'd prefer to work and get the overtime.
5. Whatever.
6. Great. I really want to have Christmas at my house.
Deal with the responses according to the emotion behind them. And then go on your trip and enjoy yourselves.