"The biggest challenge for kids is not physical, in my opinion, but mental. It can be a little boring and they lose interest. "
This is exactly my experience, and one reason I love the Sierra over the Appalachians, especially with the kids. Every five steps or so, something about the scenery changes, even if its a different lizard behind the next rock. Not so in the Green Tunnel. I have gone so far as to say kids don't get tired; they get bored. Obviously not literally true, but boredom sets in way before they run out of physical energy. Good reason for mixing it up: a stop to play around the lake or fish, identify flowers, play hide and seek with the wildlife, trade plains for peanuts, test the echo, all the things we are really out there for anyway.
