My best friend from the Chicago area and her husband adopted a boy through an open adoption. They were actually at the birth and then got their son a few days later. They were on pins and needles for those few days, afraid that the birthmom would change her mind, but she didn't. It was incredible to be there, literally from the birth to the present.
The birthmom was married, had a child already, but was in the process of a divorce. Considering the circumstances, she decided adoption was the best route.
My friends worked through Lutheran Social Services, if I remember correctly. There were home visits, group discussions for prospective parents, and extensive questionnaires. It helped them really process if this was the right thing for them. After approval, then it was just a matter of waiting. They were willing to adopt domestically or overseas, but then this adoption came up within the same metropolitan area, making it much easier and faster for all involved.
At first, I wondered how an open adoption would work but it has been great for them. On occasion, they've had to pull back a little because the birthmom wanted too much contact and it began to feel awkward, but they have since sorted that all out. As long as you have your legal and personal boundaries drawn well, it can be a wonderfully rewarding way to go.
It has been an interesting road. Their son knows he has a blood brother. In fact, he comes for weekend visits on occasion or the two families occasionally do things together. Once, when the birthmom went to a psychiatric ward for a couple of weeks, the brother stayed with them for the duration.
That was the point where they had to draw the line. The birthmom had just kind of shown up and said she was going to the hospital, without any warning. Other last minute requests had happened in the past, I think, so when the birthmom was healthier again they had a talk with her. They had a good relationship with her, but this experience was too disruptive for comfort. They drew the line and said, if this happens again, they were prepared to go for custody of both boys. However, that bumpy road has been passed and the boundaries are much clearer.
It also, prior to that experience, got a little weird at one point, where my friend realized the birthmom felt like she was going to be best friends with them all. But my friend had to put some boundaries on that as well.
That being said, it has been a wonderful experience for them. Their son is most definitely their son, they are most definitely his parents, the birthmom is more like a friend of the family as well as the brother. They probably have more contact than many open adoptive/birth parent arrangements, but it works for them. I think the contact can be defined however both sides agree to do it--cards and pictures, or more.
My friend has often said how interesting it is to know both her son and his birth brother...and, in fact, the birthmom, too. It gives her a window into how he will look as he grows older. It gives them insight into behavioral patterns and diseases. It gives their son a link to another human being with the same genetics. The boys are now 12 and mid-teens.
I would encourage you pursuing the adoption through a lawyer or an adoption agency. It always helps to have all of your I's dotted and your T's crossed. I don't know the MA laws, but I'm sure there are many. When you pursue adoption via legal paths, the boundaries are defined and it clarifies things down the road.
My sister adopted her granddaughter. Talk about an open adoption! That one had the potential to be a lot fuzzier on boundaries than my friends' situation. But it is clear to all involved, especially with it in writing, and it also works well for them.
There is also an organization in MA that makes arrangements so that the birthmom lives with the adoptive family for the last few months. They get to know each other, the adoptive family pays for all birthing expenses, etc. I don't know if there is contact after the birth and adoption, but that is another option.
Best of luck! And act quickly, if you think you want to follow this path. I don't know how long this could take, if both parties are already known. But I know my friends' process took roughly six months. My sister's process was much faster because it was relatives involved. But you may all need time to work out the specifics and to process your feelings about it all.
Good luck and enjoy!