We do studies on snappers (and Blandings and Musks) at the National Park where I work- normally from late May into July.
I presume that particular specimen was pretty lethargic? Otherwise, I wouldn't let a child get that close to one- unless I had my Glock trained on his bony skull. Just kidding, don't have a Glock.
Anyways, in warmer conditions, these things can move remarkably quickly on land, even twisting and jumping in one fast move to attack a perceived threat coming from behind.
CCB
No worries with the snapping turtle. Its about the 3rd one we have handled this year. I used to teach outdoor ed. for the conservation authority and my kids have grown up with the critters. The turtle was also more interested in me sticking my camera in its face and Victoria was well back except for her hand. She knows how far the head can come back. 
Being born a Brit and having lived there til' the tender age of 12, I can say that Carp are not unfamiliar to me. In fact, they can be one of the most difficult fish to catch. Those barbells are very sensitive, as are their mouths. You should check out some of the "Coarse Fishing" equipment available. You could easily spend 5X the money on a top notch Carp fishing outfit as compared to a Steelhead rig.