Okay, well if you're not sure about his comittment, skill, etc. I'd lower my bar a little bit and suggest this:
Bugera combo, 5 watts, sounds ok, just enough knobs to get him excited.
Buy Bugera V5 5W 1x8 Tube Guitar Combo Amp | Tube Combo Amps | Musician's Friend
Or, for a hundred dollars of fun, Sammy's beloved micro-cube might be fine for a kid.
Buy Roland Micro Cube Combo Amp | Solid State Combo Amps | Musician's Friend
I still like my other suggestions, if you think he will stick with it; those slightly more expensive, bigger amps will keep their usefulness, whereas he might outgrow the Bugera or the cube.