Two facts:
1) You're going to pass your genes down to your descendants, no matter who you marry (oops, silly me, I still think in terms of marriage and family. ah well, those who don't can adjust).
2) Your descendants are going to be of mixed race. Your children won't be, but your grandchildren may well may. And if not your grandchildren, then your great-grandchildren.
In fact, given that your family has already cracked the interracial barrier, your descendants may go interracial pretty darn soon, no matter how white you might want your family to stay. But even if your children are of the same mind as you are, given trends in American society, white, black, hispanic and oriental are all going to get widely mixed together. It's simply a matter of sooner vs. later.