Ooops! Let’s be careful with this word “destined” … there is no destiny, at least not in the deterministic sense that Eastern religions and New Age spiritualities often mean. There is God’s will and there is ours, and there is the mysterious interaction between the two.
God wills his salvation. God wills the Church and her sacraments as the ordinary means of arriving at that salvation. He is a baptised Christian and that means that he has been sealed with the mark of the sacrament of Baptism. That has consequences. On the day that he stands before God, he will be judged as a Christian, not as a non-believer, because of that sacramental mark which he bears on his soul. That cannot be ignored, though there is no reason for it to produce panic either. We also know that God is above all a merciful God.
God has given his mother the responsibility of helping him to preserve and grow in his faith as a Christian. She cannot simply shrug her shoulders and say “well, he’ll come around eventually.” He may. Or he may not.
But neither should any of that provoke panic and fear. I agree that there is likely a good bit ordinary teenage rebelliousness and/or confusion happening here, so mum doesn’t need to be overbearing or “preachy” (“in his face” as you said). However, this does not mean she should just back off and leave him to his own devices either. Her responsibility as a Christian mother is to guide him to a knowledge and love of God.
OP: Perhaps this is a small comfort right now, but I think it is not unreasonable to see God’s providence in all this. Perhaps there is a reason that God in His providence brought you back to the Faith (through the intercession of your son you indicate) precisely when He did, and perhaps that reason is because He foresaw this crisis in your boy and willed that you be the one to encourage and sustain him through the coming storms, just as he sustained and led you a few years ago. That ought to be a very comforting thought I think, though it may mean some difficult times ahead. But that is what God gives us a family for, to support and carry us so that we don’t have to make it on our own. Now, it’s your turn to be patient, constant, prayerful and firm in your own convictions and example so that he can draw strength from you.
I look at it like this: the loss of faith is a spiritual illness he is suffering and your heart is breaking the same way that it would be if he were chronically ill with some physical ailment and you had to stay by his bedside for months (or years!) and help to nurse him back to health. I don’t see a big difference here, except that the spiritual consequences of his ailment are not as immediately and physically evident as the ones resulting from a physical disease would be, and so it is easier to ignore them or imagine that they don’t really exist. They don’t seem as immediate or life threatening. But they are, and now you (with enormous peace and confidence in the abundance of God’s goodness and mercy!) have to help him recover his spiritual health.
This is the real work of a mother, imho. You gave birth to him and brought him into this world, but we know that that won’t be forever. You have to foster in him the knowledge and love of God. But that is going to take patience and prayer.
Above all, be at peace. Really. Pray for him. By all means seek the intercession of St. Monica, St. Augustine, the Blessed Virgin and all the rest of God’s family, but know that your prayers *will not *be without fruit.
Sorry for the super-long post :o ; I will pray for your intentions today.