Its sad to even know that it could come to this situation seeing as Tricare provides free birth control. However, people amaze me every day with new ways to make dumb choices.
On the bright side, this could turn in more than one positive direction. If all parties are serious about this, I would seek legal council. I dont believe there is a requirement to use an agency, so you could just hire a lawyer that specializes in adoption, and being that all parties are interested in would take a lot of the hard work out. Of course, it could cause completely new hardships if you go about it the wrong way....
Or, better yet...perhaps recommend they seek financial council so that they can keep their unborn child. All military personnel make the same money as others in their rank (Air Force wife here) so if other families live off it, they can learn too! As their friends, I would consider that direction. It sounds like a stress mess that would potentially ruin a friendship if they chose to try and regain custody in the future. Friends are shoulders to cry on, to seek advice from....not to give your child to.
Good luck with whatever happens! I would definetly take the time to seek advice from a professional....if anything, they could use some council in these trying times.