At four years of age a "Chipmunk " would be the right size and length, but consider a "Can" on the end. First the noise is reduced to not induce a flinch, and you can instruct without ear plugs or muffs. In our shop. the "Chipmunk" and supressor are a popular combination, if your state allows NFA items. A quiet .22 is loads of fun, hard on varmits.