There's not too much that you can do to control misbehaved children, if you ended up with shots that caught some undesirable expressions, you can't be held responsible for that. The parents know exactly what they bought to you for pictures.
I agree with maxharvard completely. I personally never had that issue with my own children so I couldn't even offer anything to help because it just wasn't tolerated, but that's me as a parent speaking.
At most, you can offer a re-shoot or if it happens in the future, a re-schedule if they aren't behaving at the onset.
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Lori Putman flickr
~No one can drive us crazy unless we give them the keys
~~Life isn't about waiting for the storm to pass, it's about learning to dance in the rain!
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