My son and his mate use Valken Mi-7, they are 12-13 years old. Masks fit great and as they are double lensed don't steam up. They cover the face totally and protect the ears. My son has detached the visor and wears a boonie hat over the top.
Only other thing I would recommend for a kid is something to protect the neck, my son got hit in the throat and it hurt him so much he almost gave it up. Unluckily hit but if you've got bare skin you can guarantee you'll get hit there. He now has a scrim around his neck and is fine.
Last thing, gloves. getting hit in the knuckle is painful, my daughter got hit and had a lump for weeks.