Other mistake: When the girls are in the diner and Chrissy is counting money, you see a picture of the tree house in a tree, it is the same tree as the one the girls use after they buy the tree house.
Other mistake: Really, that is one amazing tree house. Not only has it supposedly held up with no discernible weathering for over twenty years, but it manages to support four grown women, justifying their faith in bringing a newborn baby up there with them.
Other mistake: Watch when the bird poops in Chrissie's hair. From the camera angle above them, you can see that Chrissie not directly underneath where the bird is perched. The next shot shows the bird poop falling directly below the branch. The next shot after that shows the poop in Chrissie's hair. Judging by the position Chrissie was in, in relation to where the bird was, this is impossible.