Hi, Patricia! Really, the best way to purchase your Walt Disney World theme park passes is right at the theme parks or online by clicking
Disney World Theme Park Passes. You can customize your passes by adding the park hopper option if you'd like, although that will add a bit to the cost of your tickets.
There are some online outlets that offer tickets for sale, but I caution you to be very careful buying passes online. Unless you are dealing with an agency that has a good reputation, such as Undercover Tourist, you run the risk of purchasing park passes that won't work when you get them to the theme parks.
You may be able to get just a couple of dollars off by going through places such as Undercover Tourist. Discounted tickets, however, are not easy to come by!
Have a great time on your upcoming vacation!