I'm with Alex and Smiley on this one! Absolutely it's a fair boundary.
When my older brother's children were younger, he took them blueberry picking one fine day. My niece was only 2, I think, and although she was being very well-behaved, the owner of the blueberry patch approached my brother, and said "I'm sorry, no one under the age of 5 is allowed in the blueberry patch, that's our policy."
"Why?" asked my brother. "I'm watching her, and she's not causing any trouble."
"I know," said the worker. "But it's just our policy."
"Well, what's the reason BEHIND the policy?" my brother persisted. "Isn't it to prevent MISBEHAVING children, or UNSUPERVISED ones? Like I said, I'm watching her."
"I'm not sure the reason behind the policy, sir -- it's just our policy."
My brother picked up his daughter, and told the attendant "Well then, it's MY policy never to spend my family's money at a place that would have such a policy."
And he handed the guy his basket of picked blueberries, and he left with his family.
