Hello and welcome to planDisney, Matthew!
Congratulations on your upcoming
Walt Disney World Resort vacation! I know that you and the rest of your family members will have the best time.
Reading your question, I think that instead of adding the additional guest (or transferring the reservation) at the end of the vacation, why not add everyone to the plans from the start? First, add everyone to your
Family & Friends List to make it easier to plan for everyone regardless of when each will leave or join you on your vacation. Once the additional family member purchases their tickets, have them
link their theme park tickets to their
My Disney Experience account. When you make your theme park reservations using the
Disney Park Reservation System, you can choose which guest will join you on specific days. In other words, you will make your theme park reservations and include the first guest, and when they leave, include the additional family member in the plans for the last two days of your stay. I hope this helps.
Please return should you have additional questions.
Have a magical time!
Raquel