Montreal, Expo67, the Centennial World Fair, I was 9. My parents took my little sister with them to see what ever it was parents went to see. My older brother (14) went his own way. My older sisters (12 & 13) went as a pair. And I did my own thing for two different days. Met the folks at some Chinese arch or somesuch at 5 pm. Nobody thought twice about any of it.
Nowadays I would want my 12 and 14 year old boys in sight, and my 18 year old daughter would be on my mind. The oldest boy is a father himself, and a free agent