Well, I got the elastic and finished the skirts.
I hemmed up the top leaving an opening large enough to thread the elastic through.
Once the elastic was threaded all the way through, I overlapped it about an inch and sewed it a bunch of times to make sure it wasn't going to come undone.
Then I sewed the small opening closed and the skirt was finished.
Here are the girls modeling them:
The skirts are plenty long for both of the girls so I am hoping they can wear it next year too.
I couldn't believe how simple this was and the fact that I completed the whole project in less than a week was even better.