I saw both versions, the adult version just shows a bit of the knife on the neck bit, nothing bad at all ... I use to lop off the head with a hatchet.
I haven't butchered chickens for many years, but seemed to me that you boiled him a bit long ... the feathers come out pretty easy ... maybe half as much as the time you did. I used a small paring knife with a blade maybe 2.5" long, but SHARP!
After a few you learn how the bird comes apart, how to get the joints apart, and how to avoid cutting the guts ... I would make a tiny cut near it's vent, than slide a finger in the cut, and pull the skin up away from the guts, to slide my knife in along side my finger, and cut up to get a big enough hole to get the guts out, without cutting them!
Glad you had your children watch, and help!
And good job for trying this with only watching a video as a guide!