Raising children to be good Catholics is one of the most challenging (and vitally important) responsibilities facing parents.
I remember a priest one time saying, "If you want to be happy, be holy. If you want to be really happy, be really holy. If you want to be really, really, really, really happy, be a saint."
Do you want your children to be happy? Well of course you do. So you yourself must be very, very holy, and teach them how to be holy.
But it starts when they are young in the example that you set. Plant roots, plant deep, deep roots. If they're just expressing their doubts about the faith, ask them to look into it. Pull out the Catechism of the Catholic Church. That's absolutely huge.
But another thing is to pray. Parents, you have to, have to, have to pray. And I know some people get a little annoyed and, "Oh, Father, can't I do anything more than that?" Well, what's more than prayer? Prayer is much more powerful than we often realize.
So you have to pray, and pray how to talk your children. Sometimes we can say something, it'll close a heart. Other times we can say the same thing, it'll plant a seed.
Another thing is, know and when to let go. So now, if your children are still living at home, I would say, "You've got to come to Mass. When you're living under my roof, my rules, you've got to come to Mass." When your children are under 18, you know, they're your children. They do need to do what you say.
If your children leave the faith, know that that's not a reflection on you, so learn how to let go and let God. We can't save ourselves. Only God can save us. Jesus Christ is the only Savior. So we need to let go, and let him save us.