Hi Michelle!
The Princess Half Marathon is a great race! You will have plenty of time to train for the race, and plan your magical trip!
You will definitely want to stay at one of the
race weekend host resorts. These Disney Resorts will offer runDisney bus transportation to all of the race weekend events. This is a huge benefit for runners and also for their spectators. The list changes from year to year, but a lot of the resorts will be host resorts for the 2015 race that are for next year's race weekend. My favorite resorts are the Epcot area resorts (Boardwalk, Beach Club, and Yacht Club) and the Grand Floridian. These are all
Deluxe Resorts and are a little more expensive. My favorite Value Resort is the new Art of Animation Resort. It's a really fun place to stay!!
Generally, the newer events will sell out the fastest. The Princess Half weekend has added a new 10K distance, as well as a "Glass Slipper Challenge" (doing the 10K and half) for the 2014 weekend. They also added a new "Coast-to-Coast" medal for runners who do the Princess Half and Tinkerbell Half in the same year. There are not usually discounts for signing up for multiple races, but there are sometimes "challenges" (like the Glass Slipper) that offer an extra medal, shirt,etc. for doing more than one event.
I hope this is helpful! Please let me know if you have any other questions leading up to your race.