My husband and I are native speakers of 2 different Languages. Lets say mine is A and his is B. We both can speak and understand the other language - with varying fluencies. He speaks my native language (A) better than I speak his, so we speak "A" at home. It's become the dominant language for us now. So our child will definitely first learn A, and probably learn it the best. His parents though, speak only his native language - B, and we'd want our child to be able to communicate with them comfortably when we/they visit. So that's the story of A and B.
Now, we have just recently moved to Italy with our 4 month old. Once we get her into a day care and play groups, she'll naturally pick up Italian. That's already 3 languages. But we may not always be in Italy, and when we move to an English speaking country, we don't want her to be at a disadvantage. Especially if we move once she's a little older, and unable to learn a new language as easily as a toddler would. So we'd like to try and teach her English too, at which we are both quite proficient.
Is it too much of a burden on her to teach her English this early too? If not, how do we go about incorporating both English and our secondary language B into her everyday life? (I'm not asking specifically about language A and Italian, because I figure those will happen naturally)