If you are looking for the least amount of kick, I'd go with the .243. For a small kid, fit is more important than anything. If the gun fits them well, they can handle much more kick naturally. IMO the ADL would be way to big for the avg 9 year old. The model 7 youth is probalby a great choice. I was just talking about this with my brother in law the other day. He wants to get his son a gun as well(9 also). He's looking at 2 guns. The model 7 youth in 7mm-08, and handloading some lighter loads for it to tone down the kick. Or the NEF Superlight Youth in .243, .....he's looking at that also. Both should work very well, big difference in price though. Good luck!