Here are our finished Fairy costumes for Halloween.  The wing construction how-to is posted here.  Initially I was going to sew costumes out of tulle, like some of the vintage ballet costumes on our Pinterest board.  But after some experimenting I realized altering some of our existing dress-up clothes would work better.  These two dresses are old shirts.  I altered and added shorter straps to the green dress and made slits up the sides of the gold dress to allow a tulle skirt to fit underneath.  We used this tutorial from wikiHow to make a simple no-sew tulle skirt similar to this one:
The skirts are super easy to make and only use a ribbon and strips of tulle.  I ended up making a second tutu to match the wings.  Both will end up in the dress-up clothes after Halloween.  I wrapped strips of tulle around a headband for Ada’s hair.  I wondered how sturdy the wings would be, but our double layer of pantyhose survived nicely through the first of our Halloween celebration this weekend.  
We managed to finish the costumes with a whole week to spare, and Josie seems to have finally stopped changing her mind about what she wants to be for Halloween.  
Trick or Treat!