which country will make the decision

amer. moved to poland with polish wife. had 2 kids (now 1 and 3) kids have duel citiz. i've passed denial and know there is no return for us. want to take kids home to US. in poland there is big family and older is already in school. in US, no such family, would only be me and my parents. I think divorce would be mutual if i filed but she will fight for kids. when i'm ready to file what should my first approach be to taking kids with me??