I am raising my sons to be multi-lingual (German and English) and it is a wonderful thing indeed to see the mind expansion that occurs on your average code-switch .. especially in very young minds. "Daddy, the erdapfel sind too hot!", and "Das Feur makes me vv-aaaarmm!!" .. ;) Much amusement in such moments.

And socially, I think it sets the kids up a bit as well, because they are quite acclimated to the strange looks from strange people when you switch fluidly, between the languages. There is a huge caché, and the boys seem to be becoming aware of how to spend it.