This year, I was determined to get one last use out of them. Trouble was that my older daughter's was a bit too small. I couldn't get it zipped up past her mid-back. I sought counsel on Instagram, and decided to alter the dress to a v-back. It was a dead easy alteration in the end; I literally just turned the dress inside out and sewed a diagonal line on each side, from the point where I wanted the zipper to end, to a couple inches away from the zipper on the neckline.
I was worried about the zipper stop, but since I sewed my seams across the zipper tape, there was a natural stop. When I cut off the excess, I made sure to leave an extra 1/2" or so of tape in the seam so it wouldn't pull out. Then I turned it right-side out and pressed. Voila, v-back dress that (just barely) fits its owner. Below you can see the altered dress compared with my other daughter's unaltered dress.
I actually prefer the v-back to the original, and might incorporate it if I make this pattern (the Oliver+ S Fairy Tale Dress) again.
I attempted some hand-beading to gussy up the fronts of the dresses a bit. I ran out of time, so they aren't as ornate as I had planned, but the girls were happy with them.
I had decided ahead of time not to bother with making new sashes, as this was likely the last time these dresses would be worn by my girls. So I just bought some ribbon. N doesn't like to match Z, and I had initially bought red ribbon for her dress, but I thought it looked better without, so we tied it in her hair instead.