I disagree. It wouldn't be so horrible if your children were merely carriers especially since by the time your children have children embryo selection tech or its successor will be much more advanced than it is today. True, if you were otherwise indifferent between (1) using an embryo that had one copy of the bad gene and one of the good one and (2) an embryo that had none of the bad genes you should go with (2) but this is extremely unlikely to happen since if you're going to use embryo selection you should look at far more than just that one "bad" gene.