How it has been in the past. You can register for a race or challenge that is still open. Then call disney to tell them you are changing your registration to another race/challenge. Then they will refund you for the previous race less a $45 change fee. Others can comment if this has changed since last year.
Example. You could sign up for the challenge OR the half then have your 10k refunded less the change fee.
NOTE: you can add on the half but it won't count as the challenge. Only if you sign up for the challenge. (wish they'd allow you to just sign up for the second race but the extra medal/shirt must cost more.)
