No, you aren't just being old-fashioned. Instead you're being wise, and you're also being concerned about your grandchildren's future.
I've often asked myself how young children learn the difference between right and wrong. To put it another way, how will their character be shaped? They should learn this primarily from their parents, both from what their parents teach, and from the example their parents set. This is why the Bible says to parents, "Start children off on the way they should go, and even when they are old they will not turn from it" (Proverbs 22:6).
But all too often, I'm afraid, children today are learning this not from their parents but from what they see on television and in films, which is often false. If children grow up on a steady diet of violence and immorality on TV, is it any wonder they end up confused about what's right or wrong? Is it any wonder they end up believing that the goal of life is selfish pleasure?
Pray for your son and daughter-in-law, and ask God to give you an opportunity to share your concern with them - gently but clearly. Pray for your grandchildren also, that they may learn to appreciate what's good and reject what's bad. Pray most of all that they (and their parents) will put Christ at the center of their lives. And pray, as well, that as their grandparents you'll "set an example... in speech, in conduct, in love, in faith and in purity" (1 Timothy 4:12).