My first ever flight was when I was aged 7, going on holiday with my parents. Having seen far too much about crashes on TV, I recall sitting down specifically thinking "so, I'm going to die" - but having great faith in my parents, my 7 year old mind didn't trouble about this unduly.
Mind you, it was a Comet, so I may have had a point!
Which is of no help to you at-all; being more helpful perhaps you could once in a while take your son to an aircraft museum or airfield occasionally - no mention of your own flying, just to see and watch, and associate it with fun, rather than something bad.
And ration the TV, rots the mind! especially at that age.
G