We recently purchased a Ruger American Compact in .243 for a new hunter in our family. It has turned out to be nice & accurate and no complaints with it thus far. Although I am a huge fan of the .308 (have owned about a dozen over the years) I'd recommend the 7mm08 over it for someone of smaller stature. I would have gotten a 7/08 over the .243, as I think it's a bit more versatile, but could not find any in stock at the time.
Marlin also makes a decent quality youth sized rifle in their X7Y.