I'm really sorry to hear that you are suffering this way.
You asked for advice for something you can do. I want to share with you a method that I learned that lessens suffering. It is a step-by-step thought process. It helps you neutralize the emotional trauma that a bad situation causes in you.

This is the step-by-step process of how to do that. It involves taking a thought that makes you suffer. Like we take the thought, "my children have been taken from me" and first we ask, who took the children? It sounds like your wife took them, but also you feel like society is to blame for them being taken.

So we say, "Society has taken my family from me." In this process we call this the "judgement." Next, you fill out this worksheet http://thework.com/thework-old/downl..._Worksheet.pdf for the judgement of "society has taken my children from me." The worksheet asks you to answer a series of questions. Once you've done that, then you do the "turnarounds." Where you say the opposite of the statement to the other, to the self, and to your thoughts.

So you say, "society has not taken my children from me" and you think about how that could be true. Perhaps it's because the love of a father can't be diminished by distance or time. Perhaps it's because you refuse to let your children be taken from you in your heart and spirit even under any physical circumstances you have to endure.

Then you say, "I have taken society from my children" and you think about how that could be true. Perhaps it's that your view on society has being narrow minded and unkind has taken the possibilities of what "society" could be from your children. Perhaps in that you are defining "society" by their views on interracial marriage, you are limiting the way your children will be able to understand and perceive society. Perhaps by shielding your children from the realities that they might face in society, you are preventing them from developing in a way that might give them more options when they grow up.

Then you say, "I have taken my children from society" and you think about how that might be true. Perhaps it's because that by downplaying your interracial marriage, you are actually robbing society of meeting, understanding and changing their views based on interaction with your children. By giving in to society's pressures, you are taking away people's chance to change their views for the better.

This is an example of how the process works. It helps you realize that it isn't your situation that's causing you the immense suffering you feel, but instead it is your thoughts that you're believing about that situation. This process helps you disperse those thoughts and lessen your suffering. You just keep doing it over and over until you stop suffering. It really does work.

And once you are free from that terrible pain of suffering, your mind can concentrate on practical solutions, like how to make the best of the situation as it is, or how to change the situation for the better.

There's a lot more info about this method at The Work | The Work of Byron Katie