Costco.com had the best deals that I found for vacation packages/ tickets (if you are a member). Super easy to book and navigate the site. It was a lot less than Disney's direct sight for the exact same thing.
It might even be worth getting a membership for a year just to book the trip. I suspect you'd make up the cost in savings. You can look at the website without a membership.
Maybe try Sams Club too? We don't have those around here, so I don't know don't for sure, but I think it's the same thing as Costco. Or, AAA Auto Clubs will book trips like that for you at a discount, but I didn't find it to be as low as Costco. Nice that they do all the work for you though.
My Dad can get really good deals on Disney through the Navy, if you have anyone in the military who could look into it might be worth a try (buy through the exchange).