I use headlamps while mountain biking and I think you would be better off with a handle bar mounted flashlight or bike light specific for that matter. I use both. My handle bar lights are a Quark 123 turbo and a Fenix tk 15 while I ride. These lights have excellent throw for down trail/road vision and have enough spill to shine near the front tire. The flashlight "Strobe" mode is also a good functon for dusk dawn times on the street. Helps get the attention of cars(drivers). Saftey is the main concern especially if your talking about a youngster.
Don't forget a good seat(tail) light. Again a strobe function is great for geting drivers attention. I use a PLNNET BIKE superflash. It's cheep and a good light.
As far as headlamps personally I like a throwy light while I ride. You can always use a throwy light for upclose situations(flat tire repair), But a flood light won't shine that far to spot a potential hazzard in the road/trail while at speed.
If your looking for a specific Brand of headlamp any of the lamps mentioned here on cpf are excellent canidates.