Telling Coworkers at New Job

I just started my new job 2 weeks ago. I am a teacher at a HS, and I have already told the assistant and head principal. However, I am trying to decide if I should announce to my coworkers? Since I haven't been there long, I am not really close with anyone. However, the one thing is that my mom has been working at the school for 30+ years! She knows everyone and is probably bursting at the seams for everyone to know! I am 13 weeks today, so I am sure I'll start to show in the next few weeks. I just don't know how new coworkers that don't know me too well would take me announcing it. Thought I can just put treats in the lounge or something simple with a sign? Thoughts and advice?!?!