Adding a toddler (typically defined as a child under age 3) to your Disney World or Disneyland reservation is a crucial step for capacity planning and dining. If you are booking a Walt Disney World Resort Package, you can add the child during the initial online booking process by selecting the "1 room, X adults, X children" option and entering their age as "0, 1, or 2." If you have already made the reservation, you can usually add them by logging into the "My Disney Experience" app, going to "My Plans," and selecting "Change Reservation." However, for many room-only bookings, you might need to call the Disney Reservation Center directly to add them to the "Room Manifest." It is important to know that while toddlers under 3 do not need a park ticket and stay for free in your room, they still "count" toward the total occupancy limit of the room for fire safety codes. For dining reservations, you must include the toddler in the total guest count, even if they will be sitting in a high chair or on a lap; this ensures the restaurant allocates a table of the correct size. You do not need to pay for them at "All-You-Care-To-Enjoy" buffets, but the restaurant still needs to know they are part of your party.