Christine those are awesome. Your girls will feel really special, I'm sure.
I didn't do anything fun like that, but I did get my girls some nice Thank You gifts at the wedding. I had to stay within budget, but I got them:
1. earrings to wear at the wedding (each a little different)
2. ivory pashmina (my friend brought them back from India herself!)
3. Sephora gift card
4. cute keychain from Three Chickadees (in the wedding colors, of course)
5. JCrew flip flops, also in wedding colors