IMPORTANT Regulations if you are Traveling with Children
U.S. citizens traveling with minor children may be asked by immigration officials to show U.S. birth certificates for each child. When children are not traveling with both parents, immigration officials often request signed documentation to establish the children are traveling with the permission of both parents. Such documentation may include notarized letters from the parent(s), custody or adoption papers, and death certificates in situations where one or both parents are deceased.
Although sporadically enforced, we do highly recommend following these rules and regulations to prevent any issues from entering Belize. Many times, the airline will not even let you board the flight without these documents.
Please see the U.S. Department of State website for more information.