VERY well stated!!! The best breed for your child is the one that makes his/her heart sing! The whole point is for the child to thoroughly know their bird, and to train it to accept the necessary handling. Chickens are easily trainable, and while a specific bird may be easier or less easy to train, I do not think there is any breed characteristic about it. Those having problems with silkies, do your birds have clear vision? You may need to trim the feathers around their eyes so that they can see unimpeded. While a larger bird may be more difficult to handle, if that is the bird that your smaller child adores, let it be her decision, just make sure she/he understands that extra work and training will likely be needed, and that the child is willing to put in the extra time. It is fin to steer your child to a smaller breed, but if she/he insists on a large bird, that is okay. The experience gained will be worth the extra difficulty in handling a larger bird.
Showmanship is done a bit differently in different parts of the country, and walking the bird is not done in many places. Not that long ago I listened to a couple of judges talk about how different showmanship can be in different parts of the country. Likewise, age and being in 4H or FFA are not necessarily related to showmanship.