If it will put your mind at ease, it may be worthwhile to do the amnio. Keep in mind that they may find other things on the amnio, too...I've had several friends who were told they would likely have a Down's Syndrome baby or that their babies had other disorders, and then when the babies were born they were perfectly healthy. This caused them a lot of needless stress and worry, which is the main reason I did not have an amnio with Jack. If we don't have an amnio, we will probably try to see if a PO can be brought in right after the baby is born to make a diagnosis. I can't imagine waiting any longer than that to find out!
I look back on Jack's first couple of months and wish I had known about his albinism...I could have dimmed the lights more and would have been more sensitive to his squinting. If we don't find out prenatally with our next child, I think I will have the lights dimmed in the delivery room and in the hospital room until a PO tells us for sure.
I know what you mean about family members making guesses, making comments, etc. I dread that...but I also think that people will be comparing your children in many ways, so that's just one more comparison they will make. Just think about how when a baby is born, everyone looks to see if it looks more like mom or dad...if it looks like its siblings...etc. So even if they know the child doesn't have albinism, there will be other comparisons to make!
Having recently been talking about this same issue with my husband, I thought I would share the things we've been considering. But in the end, it's a very personal decision, and I don't think there's a right or wrong answer.
Good luck to you!
Amy, mommy to Baby Jack