I'm with PompeyPaul on this:
flying is about as dangerous as motorcycling and I wouldn't fly with my son unless
a) I was a lot more experienced and had to fly for some reason e.g. a farmer with a cub and a vast remote farm in Kenya whom I know of or
b) he was old enough to really enjoy it, and ideally to look after himself to some extent in case of an accident. And ideally with his mother.
I keep thinking of Neil Williams (the aerobatic pilot) who wiped out his whole family flying an IMC approach. Perhaps it's maudlin but I prefer flying by myself or with some rather lonely middle-aged friends whom I like very much but who have no close ties.
The contentedness I currently feel as a father and partner was very hard-won. It isn't an easy thing to find in life. I'm sure my partner feels that way about my son and myself also. I've met parents who've accidentally killed their children and it's not something I want to put myself, my son or my partner through.
I remember one of the paragliding magazines had a photo of a man taking his 6 month old flying in a tummy harness. One of the responses in the article consisted of the single word, 'why?'