Yesterday, my son Peter (age 5) asked me: "Why is it that some words come out in Spanish and other words come out in English when I talk?" Even though he uses mostly English to communicate with me, but often sprinkles his sentences with Spanish. ["mira, mami" (look mami) or "nónde está?" (dónde está?, where is it), or "fraza" (frazada, blankie) and "leche" (milk).] I responded that it is because he is bilingual and has many things to say-- some of which he feels better explain what he is trying to say.
I too "code switch" with them right in mid sentence—depending on whether or not the words I want to use FEEL RIGHT when I say them. In her work, Garcia (http://youtu.be/rVI41CMw6HM) tells us that those of us who are raised in bilingual communities use all our linguistic resources to express what we learn in our environments. Children use language to make meaning of these experiences and draw from a range of resources to do so.
Horner, Lu and Royster (2011) offer a similar paradigm: a translingual approach. They argue that difference in language is not "a barrier to overcome or a problem to manage, but a resource for producing meaning in writing, speaking, reading, and listening.... [it] views language differences and fluidities as resources to be preserved, developed and utilized."