With respect to gun weight, I'll interject that I don't think it's the weight of the gun that's an issue. For youngsters with underdeveloped hand strength and arm strength, I think "weight" is more an issue of balance. Handguns with longer barrels, especially heavy, bull-like barrels, are muzzle heavy and a small shooter with limited strength would likely run into difficulty keeping the muzzle up when shooting. For that reason, for any handguns that offer different muzzle lengths I would look at the shorter barrels for young kids. The mechanical accuracy will be pretty much on a par with the longer ones. Yes, the sight radius will be shorter, so practical accuracy may suffer a tad, but when teaching kids you're probably not going to be shooting at 50 yards, and not looking for bullseye, ten-ring ten-X accuracy.
For example, the Browning 1911-22 comes in a "full-size" version and a "compact" version (which is a scaled down Commander). In real 1911s, I prefer the balance of a Commander rather than a 5" full-size pistol. I would expect the same to be true for the 1911-22. Mine if a "full-size," but I bought mine when Browning first introduced it and there was no Compact version.