if you live with this worry everyday, then chances are it's going to happen... gosh, stop listening to the "experts" already... what do they know? parent your babies as if they were yours biologically... raise your kids as you've always dreamed... that's it...
WWJD, eh? Guess I'm not that holy.
Maybe I'm just a hairsplitter, but if I had been struggling to have children of my own, genetically mine, and found that my wife had given birth to the children of a stranger who was not even of my racial group (guess that makes me a racist too), I would absolutely, positively, go berserk.