Jill, I am very sorry to hear this about your father. I hope and pray that his treatment plan is successful.
The Princess Half is non-refundable. However, they do plan to offer a transfer option, the information just isn't up on the registration page yet. For other races with this option, they allow you to cancel up to 45 days before the event and for a small fee you can transfer your race fees to another race within the year.
You can call runDisney at 407-938-3398 to find out more information about that.
Also, once race capacity reaches 50%, they will post the percentages online. This would be a great way to monitor where the race stands as your situation changes. You will find the percentage on the
Princess Half Marathon website. It will be on the right in the "bulletin board" section.
I hope this helps. Please let me know if you need any more information.