... “mixed race” is just fine. I actually love seeing multi-ethnic couples, and feel it demonstrates humanity’s acceptance, maybe even celebration, of God’s creativity.
“Same-sex” couples, on the other hand ... ugh.
The thing is, it’s not “mixed race” - we’re all the same race, Human. It is mixed ethnicities, or mixed heritage, or mixed ancestors.
Skin color is a paint job.
And, just like buying a car, should be the last thing you care about before signing on the dotted line.