Andrei and I argued about bilingualism years before we even started dating.
He wasn't convinced true bilingualism was really possible, and I was determined to have a bilingual child in order to prove him wrong. I don't think I actually expected that we would marry each other, but I guess the thought of cross-cultural marriage didn't seem so far-fetched.
Of course, I'm oversimplifying the discussion. Here are some of the issues we argued about:
-Young children will get the two (or more) languages mixed up. I've seen clear evidence to this NOT being the case. Kids do mingle languages, but this happens when they either are missing a vocabulary word in one language, or a word is just easier to say in one of the languages. There's a more scientific way to say this, but basically it's selective, not a moment of confusion.
Although our kids insert the "other" language into their speech sometimes, they also have no problem distinguishing between the two. Case in point: Both of them, when still speaking only a few words, called us Mommy/Daddy or Mama/Papa depending on who they were talking to. Sophia will call me "Mommy" in English, but complain (ha) about "Mama" to Andrei. Same with "Papa," she will call him that to his face but turn around and tell me what "Daddy" is doing.
I guess that didn't really prove my point. Another example might be when David is talking about bugs and uses the Russian name for a bug because it's one he hasn't encountered in the U.S. or English-language nature shows. He's not confused, he just doesn't know the word.
-Bilingual kids will be behind their peers. I actually use this excuse a lot to go slower with school work. I don't completely agree because I think David in on par with his peers in many subjects. Even precocious in certain contexts. However, I will admit that if you run the numbers, it's hard for bilingual kids to receive the same input. If they are conversing 12 hours a day, in two languages equally, they will have only 6 hours of language acquisition as opposed to children who are exposed to one language. That's just the way it is. And it might not matter beyond a certain age, but there certainly might be manifestations in a younger child.