Before the onset of YouTube, U.S. parents had very limited options when it came to video programs that helped teach their children Spanish. There was, of course, the ever-popular Nickelodeon show “Dora the Explorer” and before that, the PBS show “Amigos,” that looked to instill the basics of Spanish into kids across America. These programs — while useful, innovative and entertaining — never allowed for full-on Spanish-language immersion for viewers, relying heavily on English as their primary tongue. Now, kid-friendly videos for language acquisition can be found on all corners of the internet with YouTube playing host to the lion’s share of the market, ranging from partially in Spanish to only in Spanish. The Times spoke to three of the most viewed Spanish-language educators for children on YouTube to see what goes behind creating highly engaging children’s content. Isa Muñoz — “Aprende Peque” Isa Muñoz, 33, had known from a young age that she wanted to become a teacher. Growing up in the Baja California city of Mexicali, Muñoz’s parents worked as teachers, as did …