I'm in a mixed race marriage - as are all my siblings (there are 4 of us), it does put extra strain on a marriage, that is the truth as you are negotiating not just the usual relationship stuff but also negotiating cultural expectations, and cultural upbringing things that are unfamiliar. And as a parent, you are allowed to be concerned, just as we are about age differences, educational differences, and pretty much all other differences, because we are parents and we don't want our children's lives to be unnecessarily difficult if at all possible.
If it helps, my white sister who is married to a man of Indian descent has a wonderful marriage, as does my brother who is married to a woman of Chinese descent. I married someone half-white and have found the cultural difference significantly difficult due to cultural expectations and various other expectations that I didn't know about pre-marriage and have struggled massively and continue to do so 20+ years in because of how patriarchal they can be.
My only advice is to support and love and support and love through whatever your children go through, you can't predict anything, you can only support them. I would tell your husband so you can both decide now how to show support together, and if the relationship doesn't last - all good, you've shown your son you are supportive, loving parents. And if it does last, then you have shown yourselves to be supportive, loving parents. If you make things difficult for your son in any way, he will only distance himself from you.