Identity and relationship documents carry that weight: the child's passport, a birth certificate naming both parents, and translations where the originals are not in English. Marital status matters as well, since eligibility covers unmarried children. Gather these early, because ordering a replacement certificate from a foreign registry can take longer than expected.
Collect relationship evidence before the deadline pressure
Check each document for name discrepancies, missing parent details or damage that would prompt a request for a better copy. If a child has a different surname, a prior adoption, or records from more than one country, raise it while there is time to obtain what is missing. Keep any existing U.S.
immigration records for the child in the same file — prior admissions, current status, school documents — so that the family's history is consistent across everything submitted. Order replacements for anything doubtful now rather than deciding later whether they will be needed. A civil registry abroad may take months, and the cost of an unnecessary certificate is trivial against the cost of a delay caused by a missing one.
Where a child was born in a third country, or where the parents' names appear differently across documents, obtain the record that connects them. Keep translations with the originals and note who prepared them, since a translation prepared for one purpose is sometimes queried when used for another and it is easier to replace when its provenance is known.