You might begin by exploring the TESOL (Teachers of English to Speakers of Other Languages) website, which offers ESL standards for PreK through 12th grade.
Explore the Colorín Colorado website for activities to use in the classroom. The Families section has many resources that would be excellent for use in the PreK classroom with ELLs from any background. The section called Fun Reading Tips and Activities , for example, has links to lots of activities that build phonological awareness and other important early literacy skills. In the Educators section, the page on Reading in Kindergarten also has many resources that would be great for PreK, as well as Kindergarten.