We are raising our children bilingually, since we are American/German. We first lived in the US, now in Europe, Austria. We follow our instincts, a number of bilingual friend-families and recently a few books that have come out on this topic. All of these sources agree that you should speak your native tongue with your kids, no matter what the other partner and the outside world speaks. That's what we have done: my husband talks Engish to the kids, i talk German. When we lived in the US our familiy language (when all of us are togteher) was German, to balance the English world out there. Now our family language is English, to balance the German-speaking world out there. Our youngest doesn't talk yet (5 months old), my son is 2.5 years, speaks very well, mostly German, a little English with his father.
A close freind of mine raised her daughter in Sweden, but is German herself, with the father beng Scottish and English being his only tongue. Their daughter learned Swedish through daycare and Kindergarten only -- it was not spoken at home. She was fine. Now she is fluent in Swedish, English and German. The father still knows only English, and the mother became fluent in Swedish, in addition to german and English.
I think the books and my experience suggest that you talk polish to your child always, except when in a grop with English-only speakers. That would mean that your shild starts speaking polish, but will surely catch up with the English quickly and completely as soon as going to an outside-of-the-family daycare.
Trust the remarkable flexibility of children. Good luck!
D.