The dates for Children's Week should be correct in our Minipets Events Calendar
(April 28 - May 5), and a rough time frame is provided in the Guide to Children's Week
(first week/beginning of May).
WarcraftPets generally does not monitor or update user-written guides (unless they are categorized under "official" or Community Guides), so if the guide you're referring to is a user-written one, it may not be up-to-date.
If you find an incorrect date for Children's Week in any of our official write ups, let us know and we'll review it. Thanks!