I started mine with a gerber, the little folder one. It's under $20 and i took the sharp edge off 1/2" of the tip. The rest stayed sharp for a few months. Then resharpened it up.
Hands are delicate, and a youngster can cause a lot of damage. Taking that edge off the tip seems to have worked, mine didn't cut themselves with theirs. (better than i could say for myself or my friends at that age)
For their 10th I got them a Gerber multi-tool if they didn't loose the other.
Good luck, and keep plenty of band-aids and hydrogen Peroxide on hand.