Check and see which performers will be at the Flower Power concerts while you are there. Definitely check out the butterfly garden - I missed it last year and regret it.
The topiaries in Epcot are amazing - I have so many great pics of them. Someday I'll get around to printing them out, LOL.
I'm sure you'll get many more suggestions, but at least you have a start!
ETA: Thought of another one: There's a ladybug release every day (I can't remember the time, I think it's in the afternoon) I'm sure your DD's would enjoy that as well.