I don't think I'd get too concerned about spine. If you're getting them at the local store a light flex in the hands will tell you if something is a steel bar or a noodle totally diferent from the others. If you order them, just use what you get.
You can get 1/4" nocks and field points that work great. Keep the feathers proportionate to the smaller size and you're good to go.
Best thing about these arrows is they're cheap and they'll shoot fast enough out of a small bow that they'll stick in most targets. That's very satisfying for a kid. Nothing more discouraging than having your arrows bounce off the target, eh?
Guy