OP -
That said, the airline does not need to guarantee those seats, and my experience has been that there are some friendly people willing to swap seats and others who won't give up their window/aisle/lucky row number to let a toddler sit with his mom.
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Except She isn't talking about toddlers an 8 yr old is hardly a toddler. Yes if you truly have a toddler you can usually find someone who will switch so you can sit with your 3 yr old but good luck with an 8 yr old, I wouldn't even think of asking.
Heck by 7 mine were sitting by themselves on purpose so they could all have window seats! One woman saw my son and said oh I'll switch so you can sit with your Mom and he said no thank you I picked this seat. I thanked her for the offer and she sat down next to me and chuckled.