It sounds like so much fun. I've always wanted to do this. Definitely do the character meet n greets and enjoy getting to be the "kid" for a change.
If I had the chance to go on a girls only trip, I know I would go get pedicures over at the GF spa on the day I went to MK. It would be such a nice midday break. I would also browse the stores in world showcase more (DH hates to shop). I would also do a character meal because no one except for me ever wants to do one.
Enjoy your trip.