Holidays during deployments can be tough. Fortunately your son is young enough not to have a good strong grasp on days yet, so I'm going to suggest what I did with my kids when they were the age yours is, and that is call the day you guys get to talk to daddy Christmas.
It really only worked with mine until they were about four, but after that we started doing other things. Like we have a different Christmas tree for deployments (this glowing white monstrosity I let the kids pick out), and the kids have agreed to wait on opening presents until daddy's around to see too. So if it's later in the day, or even the next day, they're willing to hold out just to be able to share that time with daddy. What gets me is that they came up with that all on their own.
Heck, one year we put off Christmas until mid January (Santa was very understanding and made a special trip ^_^), because that's when daddy was coming home and the kids wanted to do that.
Being in the military takes a whole lot of finess when it comes to every day life, let alone holidays. Sometimes you get that time, other times you don't. But you always have eachother in the end, and often times, that's all that counts. I do suggest lots of pics of daddy up and around the house. If he has a favorite cologne, spray that on a pillow or stuffed animal.
Just know you're not alone, even if it feels like you are. Many of us are in the same boat, and you'll always have support even if you think you don't. Good luck and Happy Holidays!