Needing advice

My husband and I have 3 kids, but the 2 oldest are not his biological children. My ex allowed us to take the kids out of state and we arranged it where he would have summers and I had the school year, and now my husband has projections for Germany and my ex said that I can’t take the children out of the country.

He suggested that instead of me having them for the school year, that we keep the same arrangement but reverse it, where he keeps them during the school year and I get summers. Idk what to do...we have never been to court, because we have always made our own arrangements. My oldest said that she doesn’t want to live in Germany, and that even if I stay behind that she wants to try and go to school where her father lives.

In any way that I look at things I see someone missing out. If I stay, I get to see my other 2 babies during the weekend, but my husband will miss out on the baby. And if I go I will only see my kids during the summer, so we’ll be missing out on seeing them 😢 my husband and I have been apart for more than a year already, and it’s taking a toll on our marriage 😭

***my ex is an amazing father to our kids, and the kids adore him, and I know that they’re going to be taken care of, I’ve just never been separated from them and it makes me feel like a bad mother. He also said that we can get passports for them so that they can visit us in Germany during the summer, and that he will help pay for one of their plane tickets.