It may be there that they first come in contact with those other mentors and new friends who will introduce them more concretely to the possibility of a life of total dedication. These are just a few ideas. You yourselves will have others. Nobody knows your children better than you do or loves them more save God himself. Vocations are a supply -side phenomenon.
Supply creates demand.
Don't forget the shortcut of entrusting them to Mary, the Mother of God. If our Lady takes a special liking to them, her Son will form them into the new evangelizers of the third millennium. You will lift a hymn of thanksgiving to God for rewarding your generosity by calling one of yours to be a special one of His. Don't worry, your grandchildren will. You cannot outdo God in generosity.