A multi-pump 1377 (or 1322) can get some reasonable accuracy. Although it does have a longer barrel.
A metal co2 pistol that cycles the slide can get you at least some movement.
You can also get a phone app that uses the camera to score your shots.
If this is to be expected from your family, maybe you oughta pack an airsoft or paintball gun along with a real one - something you CAN shoot him in the nuts with.