According to Official Guinness Records,
The longest career as a children's television host is 44 years and was achieved by Xavier Lopez a.k.a Chabelo (Mexico) who has hosted, En Familia con Chabelo, broadcast on Televisa, Mexico, every Sunday from 6 December 1968 to 16 December 2012.
For a complete list of Unknown date records, please visit Unknown date Guinness Records in Mexico.