As you know, my own view is that there should be a "high wall of separation" between the Parents' authority over their children, and the "interest" of the State... a sacrosanct "don't tread on me" realm of parental authority, to be breached only in cases of outright Parental Abuse, etc.
As for Adoption, there really isn't any "libertarian dogma" on the subject of which I am aware and I tend to favor the formula of assigning Adoptive Preference to the extended biological family, in order of biological relation (this is what I call the "Braveheart" formula. I also happen to view this as the Biblical formula; correct me if I am wrong).
Admittedly, such a biological Adoptive Preference would create a situation in which Adoption by Homosexuals would be relatively difficult and uncommon (with the exception, I guess, of the occasional "gay uncle" who is the closest surviving relative); but I think I can live with that, even if the lavenders can't.
My point was if biological mom lives with 4 other women during the raising of the children each of those four other women will have visitation and vacation rights (not to mention the biological dad)
Pity the children