[spoonybard]

If you're doing it according to the JLPT, you will most likely only be able to speak formal Japanese, which is fine, because of the politeness, however, according to a fairly large amount of people, if you are really familiar with a Japanese person, they get offended if you use polite Japanese. In other words, there are two types of Japanese; formal, which is more likely than not the one that will be used more often, therefore is taught most, and informal Japanese, which is used amongst close friends and unfortunately in most anime, which means that watching anime for the purpose of learning Japanese is really not the way to go, although I would imagine that the stuff made to educate kids would be different.

I agree with kirakira; hire someone that can speak fluent Japanese to take care of the kid, and you may also learn a fair amount of things as well. Also, you should probably go to a university that teaches the language so that you can learn it to where you can pass the JLPT 1 test, but remember that they call it "almost native level", because of the two different types of Japanese, and the informal stuff can only really be learned through speaking with the people from whence the language came. If you do take a university coarse, the teacher may also be of help regarding teaching the language to a baby.