It's my recent Ex's Bday today, should I text him?

Well, we broke up just under 2 weeks ago. We didn't date long, just a couple months. I broke up with him and I don't think he was very happy about it (understandably). We talked about getting back together but he decided not to. Anyways we have not talked much since except one time when he texted me asking all these questions and I tried to call him the next day and he didn't want to talk. He was being hot and cold and moody and thought I was mad at him (I wasn't but he couldn't seem to understand that). Hahah ok, anyways, it's his Bday today, and I want to send him a simple "Happy Birthday! :)" text, mostly to show him I'm not mad at him and that I do want to be friends, or at least on good terms. I'm just worried he will take it wrong, since he seems to take a lot of what I say wrong... advice? Oh and just for the record, we're in our early 20's. I will probably not run into him or see him around.