Lodging Choices: The single tip that saved us the most cash was from other parents who'd used MouseSavers.com for finding special low rates on hotels. That's how we found a rate well under $100 per night that included free internet access, free hot breakfast each morning and free shuttle to and from the parks (which saves about $14 per day in parking fees). We were content to be about five miles away from the Disney property, without feeling the need to stay in one of their resort hotels. For others who find an on-property hotel important, the discount sites sometimes have good rates for those, too.
Food Choices: The second best money-saving tip was on avoiding overpriced park food. I found that and several other useful tips from Siobhan at Wee Warrens. We ate a hot hotel breakfast each morning, then took Siobhan's advice to pack our own lunch, snacks and water so that we never felt the need buy lunch inside a park. We also kept enough food like bread, peanut butter and applesauce packets in our hotel room that we could sometimes fix a quick evening meal when the kids were too tired to eat out. When we tried one dinner inside Animal Kingdom at Rainforest Cafe, we learned the hard way that we should have just let the kids share some of our adult meals instead of paying way too much for the overprocessed kiddy food. A lower-priced restaurant choice that included real, fresh foods, even for the kids, was Chevys Fresh Mex near Downtown Disney.
Dress-up & Souvenir Choices: I was thoroughly appreciative of Siobhan's recommendation to bring your own children's costumes for dressing up. I took that to the extreme by not only bringing a pair of like-new mermaid costumes from last fall's costume parties, but by also mending two well-worn Cinderella dresses to take along. Because I cautiously read every ingredient in bath and body products, I cringed when my daughter announced she was interested in buying "princess lipstick" at the park. I headed off that conflict by turning one of our favorite brands of natural lip balm into "princess lipstick" with stickers. I realize this sort of diversion only works with the smallest children, but I'm happy to get by with it this time. I temporarily overlooked the ingredients on hair products in order to purchase our own glittery hairspray before the trip. The girls had the experience of dressing up twice in their costumes, doing their own hair and nails, and prancing into the photo studio at Downtown Disney for professional photographs with Ms. Susan. We came home with two souvenir princess folders with some glamour photos in each outfit, for around $60. Even if you add the cost of new hairspray and pink nailpolish, no more than about $70. Two new costumes each, along with two visits each to the boutique that offers hair and nail services with the photo package, could have added up to $800. For those of you with slightly older girls who might notice every little detail, be aware that there is a tiara and princess sash included in those pricey packages. We brought our own tiaras and headbands. While my girls didn't care about the sashes, a crafty mom could make one at home from wide ribbon. I understand that some people want the photos in front of certain Disney spots in the parks. We preferred the simple backdrop with what we thought was the best photographic quality at the Downtown Disney venue. We also brought along some of our own character-inspired clothing for casual dress times. We found low prices on good condition character swimsuits, pajamas and t-shirts at better thrift stores near home. A friend gave the girls new princess headbands to take along. The few things we did buy new at the park stores were planned gift purchases that the girls were able to make within a budget. 
Overall: Our family of four was able to spend a little over four days at the Disney parks and stay around our budget of $2,000 total. With some all-inclusive packages, more dining out, and salon visits, we could have easily doubled that cost. We also saved by going right before one of our princesses turned 3, thus no park admission fee for her!