I wasn't going to comment again on this topic, but since it has continued I'll chime in here to add my agreement to much of what you said. MANY people have told us what a "great thing" we did by adopting our first child and again by adopting our second child (which will be completed in about a month). We've never really seen it quite like that. They are our children and nothing more. Adoption is simply the way God has added to our family. From our perspective it is essentially the same as having them by birth.
We never viewed them as some sort of ministry or something unusual for us to do. Neither did we view them as some sort of "calling." When the time came that we desired to have children we immediately chose to adopt. There was never even a consideration of anything else. My wife has never had the slightest desire to "birth" children...it is just something that is not in her. Similarly, I've never felt any desire or need to pass on my seed or live on through my children. My child is my child regardless of whether or not she shares any DNA with me. The need or desire to have biological children is a concept and desire kind of foreign to me. It simply doesn't matter to me or my wife. We had the desire for children, the financial means to become parents to a child who desparately needed some, and therefore we prayerfully considered the adoption location and method to use and then did so.
Our second adoption has been essentially the same story, except that this child has some special physical needs. We desired to have another child and therefore adopted again, but thought it would be good this time to have a child who might be in more serious and immediate need due to her special challenges, which other parents might have a more difficult time dealing with. Again, we had the desire, financial means, and the disposition to deal with the issues and accept and love the child completely. From our perspective it is as normal as can be and we can't imagine feeling any differently.
Intellectually I can see that, yes, God has called us to adopt and sovereignly chosen to give us children this way, and we feel priviledged every day that he has done so. However, we never "felt" called or viewed it specifically as a calling. It has always seemed so normal to us. In the same way that the typical person desires to have biological children we have always desired to adopt children.