I've now made 2 Hopscotch dresses for my 8 year old and she's asking for a 3rd! For the neck opening, I cheated and used FOE (Fold over elastic). It worked great! Here are links to the pictures (hope it works)
Emily
http://s199.photobucket.com/albums/aa288/emtravford/?action=view¤t=IMG_1498.jpg
http://s199.photobucket.com/albums/aa288/emtravford/?action=view¤t=IMG_1498.jpg