You could just wait and let them figure it out for themselves.
(Please don't do that, they'll never forgive you.)
Wait until the second trimester has started. There is a chance of miscarriage between now and then, and while that will be awful, it won't be as bad as telling everyone she's pregnant and going thru all that AND THEN having to tell everyone she miscarried.
Having the child adopted is still an option if you two feel you're not capable of raising a child at this time. I know there's no way I could have raised a child at 19, I couldn't keep myself out of trouble back then.