I have wondered who is holding up the bunny ears in this photo and who took it. If that is indeed Stanley Dunham and Obama Sr., them perhaps Stanley Ann is doing the bunny ears and Madalyn took the picture, or this could be reversed.
To me the glasses on "Obama Sr." in this photo and the ones in #26, look different than his glasses in #25, although it is a little hard to tell.
Basically I don't see anything in these photos that indicates they are photoshopped. To say that they all are is totally paranoid IMHO.
The small Obama head in the Uncle Payne photo could just be a result of taking the picture very close to the foreground individuals and Obama being a little further back. The "macrocephallic" photos could just be due to the fact that Obama does have a bigger head than some people.
Assuming that some of the photos are from his high school yearbook, obviously the other owners of the yearbook would notice any alterations.