Children under three are considered special guests of Mickey Mouse and do not need to have admission to enter the Theme Parks. You will not be asked to prove your child's age, so don't worry about bringing their birth certificate or any other important documents.

For the vast majority of guests, a birth certificate is not required to enter Disney World. Disney operates on an "honor system" for children's ages. However, there is one specific exception: if you are claiming that a child is under 3 years old (and therefore entitled to free entry and free dining at buffets), and that child looks significantly older, Disney cast members at the gate are permitted to ask for proof of age. While they rarely do this, having a digital photo of the birth certificate on your phone can resolve any disputes instantly. For children aged 3 and older, you simply purchase a child's ticket (ages 3–9), and no ID is needed. It is also worth noting that if you are traveling internationally to Orlando, the child will need their passport, which serves as the ultimate proof of age. For domestic travelers, the only time you might need a birth certificate is for certain "Florida Resident" discounts if the minor doesn't have a state ID, though usually, the parent's residency is sufficient for the group.