Dear OP,
You didn't ask and this post is not handguns. But.........
You mention you have the "long" guns covered. If they are in fact, long, they cost you about 5 years of learning experience with the children. At a time when they can be taught. The handgun inquired about is a secondary learning tool compared to the rifle. In the early 1990's, an Anschutz Woodchucker taught my kids and, more recently, grand kids to shoot. First with open sights and then a small red dot made it simple. Put dot on target, pull trigger. Very short proportional stock and about 2.5#.
The closest equivalent today is the Savage Rascal. 2.5# and very short. The Accura-Trigger came at 2.5# pull and I wish every factory gun had a trigger that crisp and usable.
The Rascal has good set of post and aperture sights on it. Adjustable for windage and elevation.
The sights are adjustable and are missing only index marks. Readily supplied with a bit of fingernail polish. If you worry about cosmetics with 5 year olds, don't bother teaching them to shoot.
Photo: Rear sight elevation adjustment. Index marks noted. A quarter fits the slot. No screwdrivers. When done, use pliers to turn quarter gently tighter.
Photo: Rear sight windage aperture. The knerrled aperture unscrews to move the sight and then tightens to lock it in place. Padded pliers tighten it to avoid accidental movement. Or fiddling by little fingers. If the polish dot is broken, something happened.
Photo: 25 yards with CCI Blazer 40 grain round nose high speed. Only ammo tried. 10 shots. 5 in the center hole. Not bad on a cold and windy day. The Blazer is a good cheap reference ammo. Most other 40 grain round nose high speed ammo's shoot within its group size.
For starting kids out, CB caps make almost no noise and limit range. Not especially accurate, but useful.
Besides being useful, Savage is nearly giving them away. Dick's and Cabelas have sales on them in the $129 range. Savage has a $50 rebate. Best $79 you will ever spend.
With young children, middle children, and especially cocky young teenagers, impressing them with the destructive power of a pee-ant looking .22LR takes some thought.
Photo: Pick an object about the size of their brain and let them examine it.
Photo: You carefully pop it dead center with a .22LR HV HP.
Photo: Let them examine the result.
Then ask them if they can put it back together again. They get the idea.