Hiya Daniel!
Welcome to planDisney, and thank you for sending us this magical question. Wow, Daniel, your nieces and nephews are truly so lucky to have you! It sounds like your family will have such a magical time, so let's talk about how you can make it even more magical by adding more plans to this vacation.
Since your nieces and nephews are under 13 years old,
their profiles will have to be managed by an adult, and only that adult can manage plans for those profiles. Therefore, if you will not be present during their vacation, I would recommend that their father creates and manages their profiles in his
Family & Friends List. Children's profiles may not be transferred to another Guest, and creating more than one profile is not recommended to avoid any issues or confusion.
Now, since you have already purchased their theme park tickets, you can simply transfer them to your brother's account. Indeed, theme park tickets can be reassigned at any time as long as they have not been used. This can be done by going into "My Plans" under the
My Disney Experience tab on the Walt Disney World website and clicking on "Tickets, Passes & Memory Maker." There, you should be able to view the tickets you purchased for your nieces and nephews and reassign them to your brother by using the drop-down menu next to the ticket. It is important to note that Guests can only have up to five tickets assigned to their profile simultaneously, so it may be a good idea to plan ahead if you need to transfer more tickets.
I hope this was helpful, Daniel, and that your nieces and nephews are going to have the most magical vacation ever on their next Disney trip. If you have any other questions in the time leading up to your trip, please don't hesitate to reach back out! You've got a friend in us here at planDisney.
Have a magical day,
Ariane