Hi Eileen,
I can identify with your frustration about your son not believing. I may have mentioned this in another thread before, but I find that some of the worst people (worst is probably an overly negative word, but I can't think of another) at sharing the Gospel and inspiring none believers, are believer's themselves. My advice would be just use what God has left us with in the Bible. In scripture, Jesus Christ used some very deep spiritual cryptic parables when addressing the multitudes that believed on him, and also with his closest apostles. We all know why he did that. Paul, Peter, James, John and Jude did the same in their epistles. But, when addressing none believing Gentiles many times they just kept it simple to begin with, and I believe this is what we should do when given the opportunity to share the Gospel with none believers that God brings into our lives. Sometimes answering a question or an objection to the faith with a question can inspire people to actually think about it more.
Next time you have a conversation with your son, ask him "OK, if the Bible is not true and Jesus Christ is just a story made up 2000 years ago.......explain the last 2000 years of human history without Him. Play "atheists advocate" and lets see how far you get in the last 2000 years of human history without Christ. The development of the European continent, the near east, the Russian/Balkan continent, the USA, and in the last 200 years many parts of Asia owe their society, their history, their culture, just about every aspect of their lives to the very existence of Jesus Christ and His teachings and influence. Government and monarchy alike all over the world have been structured and hugely influenced upon Biblical principles. So, without Jesus Christ there's a huge hole in history that needs to be plugged with something." The secular historian or atheist is then faced with some pretty ridiculous possibilities. There's a lot of very compelling evidence you could present to him. Such as the Gospels and NT writings, both canonical and none canonical, were all written relatively very shortly after the events, much of them by eye witnesses. The people responsible for the NT scriptures we have, and the none canonical writings were faced with deadly opposition from both Jews and Romans, and yet they risked persecution and often execution to share and spread the gospel with the early emerging Church.........and they did this for something that was made up? That's a ridiculous notion when you think about it. Jesus Christ is by far the most reliably reported and written about person in ancient history. No other major figure in ancient history had so much written about them so soon after the events as Jesus Christ. Some scholars put some of the the book of Acts as early as 40 AD, that's only 6 1/2 years after the events, the rest completed in 61 AD. I believe there is evidence in Acts that Marks Gospel was earlier than the date widely accepted by scholars of 50 AD. Whatever the case, all of the NT scriptures were finished by 90 AD, less than 60 years after Christ was here on the earth. Atheists like to point out that Jesus Christ was not written about until "decades" after the events, as if this is an unusual length of time. The fact is compaired to other figures in History such as Alexander, a decade or two after the events is nothing. Not a word was written about Alexander until almost 500 years after his death, yet no Atheist doubts his existence or questions the stories about his conquests.
Some atheists such as Prof Richard Dawkins acknowledge that Christ existed because the evidence is overwhelming, but claim that He was mearly a charismatic spiritual leader who was very influential, that didn't perform any miracles, that was not the son of God or born of a virgin, that He didn't rise from the dead and ascend to heaven. Well with these kinds of atheists, when answering their objections we always have the premise that Christ did exist, all answers and objections have to take that fact into account. So starting with His conception and birth, the atheist has to then assume that Mary was a liar, that she risked being stoned to death for a secret sexual liaison with an unknown person.......highly unlikely. They also have to assume that Joseph, described as a just m,an in scripture was a liar, whom also risked very severe consequences if they were found out. They have to assume that both Mary and Joseph kept up the pretense to the end of Jesus' life. A number of times in the Gospels Jesus is referred to by people that knew of Him and His parents as "the son of Joseph", and so we can deduce that it was common knowledge that He was thought to be the son of Mary and Joseph and people knew this. By inspiration of the Holy Spirit, and with the help of the Holy Spirit Mary and Joseph kept His true identity a secret until the wedding at Cana. I do not believe they would have managed to have kept such a secret if were of a sordid nature.
Dealing with the miracles, again the atheist has to assume that the sometimes thousands of witnesses were all taken in at exactly the same time by some kind of slight of the hand or magic trick. Just how you get a man to walk out of a tomb after many had seen him dead, and do it all by fakery or trickery is beyond any reasonable explanation. Some would argue that the whole story was made up and never actually happened. Ok then they have to explain why it was written about so soon after the event and no one came forward to say it was fake. We have to assume that those reading it in the early Church believed it, why? Because there were probably many witnesses still alive who had this event still fresh in their memories. Would anyone forget such a thing as long as they lived and had a sound mind? I think not.
The atheists that accept Christ existed tend not to contend His arrest and crucifixion, however the events afterwards they do. Again they have to assume that the very people that had run for their lives and abandoned Him, were suddenly so emboldened as to risk crucifixion themselves for something they had simply dreamt up, a hoax. We know that many of the Apostles went to a horrific death pronouncing Jesus Christ as their RISEN SAVIOR. Is it reasonable or logical to assume that these men were responsible for the greatest hoax in history and were willing to die a horrible death defending it? No, its a stupid suggestion. Its far more reasonable to conclude that these men were so emboldened because of what they had witnessed with their own eyes, Jesus Christ risen from the dead, amongst them and showing them His wounds, and later visited upon by the Holy Spirit at Pentecost.
I hope this helps you Eileen. I've put these issues to none believers a few times and I find more often than not it gets them thinking more seriously about Christ, rather than just dismissing Him because of foolish ill thought out objections.
May God bless you
David.