1) I purchased on sale t-shirts from Disneystore.com for the girls and I, this helped tell them where we were going, and we wore them on our first day there.
2) I also picked up autograph books (for cheaper than they sell in the parks, for the same book).
3) And Princess PJ's... all on sale and free shipping
4) And I handed these out over the course of the trip, so the kids got stuff and I didn't go poor.
5) I packed individual packs of goldfish, pretzels, and nutragrain bars knowing we may have to wait or be out and about when one of the girls (or I) was run down.
6) I also brought Tinkerbell Tupperware cups with lids that I kept stocked with water for the girls.
We did splurge on Princess dresses and accessories at the park. Lots of folks had mentioned packing your Disney dresses to take with you - ours were all beat up and in fact none fit Aubrey anymore so getting news for dinner with Cinderella make it that much more magical. The girls really took their time and looked at everything in the store over and over and over again.
We all want to go back and it really was amazing how well run the parks and resorts are.