It's reasons like this I don't mind if I don't see the rapture in my lifetime. He was longsuffering with me, and He can certainly be longsuffering with others after me.
Keep your son in prayer for salvation. Never give that up.
There seems to be a theme in the Bible, and that is the Lord is in the business of saving households. Through the OT, and even with Paul.
Believe on the Lord Jesus and thou shalt be saved, and thy household.
Keep on praying. He's listening. Hold fast, and take comfort. In many cases, it may just take longer than we'd like for someone's salvation.
I know the feeling though, only in my case, the person is a little younger. We may very well be surprised with delight one day.
Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear.