The pattern for these dresses is one that I've sewn many times before. First for my own girls years ago, and then again for another friend's daughters several years ago. The pattern is still available in the pattern book, and I may just buy another to replace my worn and used copy.
The pattern does run wide, but that's okay for a costume like this. The girls will be able to wear them for several years, I imagine. (I do wish I had made the sleeves a bit longer, though.)
The doll clothes is also a McCall's pattern, number 3627, and fits 18" dolls.
I love this picture....reminds me of Holly Hobbie!