1. Usually it's cheaper to stay off site. We rented this house and were very impressed with the cleanliness. We split it a 6 bedroom between 3 families and it really reduced our per night cost, we had a ton of space, a private pool, kitchen, laundry and we could drive up and unload the kids instead of schlepping through the parking lot. You do have to take into consideration the $20 a day parking fee if you stay off site. (Our parking was included in the season passes)
2. We signed up for a Disney Visa credit card. They offer a $200 credit, but charge a $50 annual fee. This gave us a net $150 credit. We purchased our 4 annual passes using the Disney credit card and got about $75 in rewards for purchases at Disney. There are other perks including a special meet and greet for Visa card members.
3. We bought night time items for the parades and to keep our group together. This is what we purchased on Amazon and were happy with the products. These really helped to keep track of the kids and join in the glowing fun of the night at the parks.
4. We bought these kids thermoses and filled them with boiling water for 10 min (then discarded the water) and added hot mac n cheese, pasta or hot dogs (left those in the water after cooking them). The food was still piping hot and we saved a lot of money not having to purchase them lunches they may or may not eat - depending on their mood. It was also nice not to have to wait in lines for food when they were hungry. Disney has lots of silverware and condiments that you can use. My husband waited in line for our food while I set the kids up at a table and by the time they were set up and eating, he was back with our food. We saved about $20-25 a day doing this. We also brought many other snacks in our snack bags.
5. Any counter service restaurant will give you a free cup of water, we brought water bottles and saved a lot of money on water. We also brought some bottles of cold and frozen water to have in a pinch and put them on our stroller. Read more about how we packed our stroller here.
6. Because we purchased annual passes we also received a discount of 10-20% at certain restaurants and shopping at Disney. Annual passes also included Disney Photo Pass, which we loved.
7. We did the Bippity Boppity Boutique, which is pricey - but we saved some $ by purchasing their dresses in advance. We told the kids that their fairy god mother delivered them, which added to the excitement of the day when they wake up. You can purchase them at the Disney Store on sale, online or second hand for cheap. Kids don't check for tags, so you'll be in the clear.