I am with Jeff,Jeff Reardon said:I'd go for a gas gun for the light recoil, and for kids that young, you want a youth sized gun. There are a pile of used Remington 1100 youth guns kicking around, and I think they still make new ones.
Another good option, though I don't know if they are available in youth guns, would be something in the Beretta 390/3901 line.
Lots of other options out there.