I'm not sure as a 10 yr old I had heard of the River Amazon (my schooling was pre-rainforest fretting), but I would have heard of W H Smith, which was the big book seller of the time.  So I don't think the children's response was surprising.

If you asked pre-schoolers about MacDonalds, they'd likely say the fast food outlet rather than the farm.  Most will have been to a MaccyD but few will have met a farmer.