Thanks to all of you who offered suggestions on how to make shirring work for me. I pretty much tried everything you suggested and--it worked!
Unfortunately, I can't attribute my success to any one thing, but I'm just thankful that it worked and I made two new dresses for friends to show it. Here's my lovely friend Shannon modeling her new sundress. She loved it so much that she's coming over tomorrow for a marathon session of dress making--God and kids willing.
I cannot recommend this pattern enough. If you're on the fence--make it. It almost makes me want to keep living in the tropics so I can wear them everyday. Almost but not quite. It'll look just as cute with a cardigan.