But I wouldn't disagree with you on that. You can pretty much stop a small child from drawing on the walls by staying with it all the time to supervise it. There's no excuse not to.
You can keep a small child quiet 90% of the time by reading, feeding, talking through all the pictures on the camera and so on... but if they decide they want to scream and yell there's not much you can do... They don't allow Laudanum on international flights.
My then 18 month old son and his Australian grandparents were lucky enough to meet at a point when he was just old enough to enjoy the experience and his grandfather was fit enough to go to the beach with him and on trips to the national park to see 'guroos'. Next time he goes, I fear his grandfather won't be able to make it out of the house. His granny's not getting younger either. I think it would have been wrong to deprive any of them of the experience.