Hi Sharon! You are going to love the Princess Half! It was my first race in 2009, and I haven't stopped running since!
You will be running through Magic Kingdom around mile 5. When you arrive there will depend on what corral you begin in (they start about 5 minutes apart) and how fast you run. You will know your corral when you pick up your bib. Just add your pace at 5 miles plus your starting time to get an estimate of when you will be on Main Street USA. Keep in mind that they should allow at least an hour travel time on the monorails to Magic Kingdom. They can sign up for runner tracking to follow your progress through texts or emails. You will get information about that closer to race time.
Here is the official weather policy. The entry fees are non-refundable or transferable:
Weather
The race will be held rain or shine. If there is lightning in the
area the race will either have a delayed start or, depending on the
intensity of the weather, be cancelled. The determination will be
made by the Event Management staff.
The Walt Disney World® Resort Lightning Policy
Event operations will shut down when lightning is 10 miles out from
the event areas. Event operations will not resume until the lightning
is 10 miles out moving away from the event areas. Sports Manager will
determine this using the *Flash to Bang Rule* and weather radar. The
Sports Manager will consult with Walt Disney World® Resort Management on a course of action to utilize the operational rain plan, delay the event, or cancel the event.
Please let me know if you have any other questions!