Everybody seems to favor the heavier bullets in both 308 & 7-08, but your daughters may favor something lighter. Somebody in the bunch is bound to be recoil-sensitive. 120's in 7-08 should thump the shoulder significantly less hard than the heavier 308 bullets do, and 140's may be just fine, too. At the ranges you mentioned, these lighter 7mm bullets ought to do OK for you. I'm kind of sensitive to recoil, and in my old 308 I could tell the difference between 150-grain & 180's when I shot them. It was a pretty light rifle, and the heavier bullets recoiled noticeably more. The rifle weight and recoil factor would have me leaning toward the 7-08 in your situation, mainly because your daughters will be using it.