I've done that! It was on what I think was my first commercial flight, a 767 from probably YVR to LAX sometime in the early 80s. My grandfather was the king of getting kids into fun places, he would go talk up the crew (of the plane, ferry, train, whatever), then come back and fetch whichever grandkids he had.
I did the same on my first flight, England to America. I was very shy with the loud American pilots, but I'm sure I wasn't the first shy English boy they'd met.
This was in the mid 1990s, and the cabin crew invited me to look. I don't think there were many children on the plane.
Sadly those days are long gone now.