Before worrying about what others will think of you, remember this is not about them. What you decide to do in your unplanned pregnancy is your choice. Who you tell and share this detail with is also entirely your decision.
Know your audience. Trust your gut. Not everyone is entitled to know details about your life. Some people are misinformed and need to be educated that adoption is a selfless act of love from one to another.
There should be no shame in choosing adoption.