The chain guard question is tricky. Obviously (or maybe not so obviously) there's a very real risk of removing a finger with non derailleur bikes, especially fixed gear bikes. When I teach repair I remind folks of the hazard by demonstrating with a carrot. Years ago, before derailleurs were dominant, you could often spot a bike mechanic by the missing finger tip.

OTOH, chainguards typically only cover the upper loop, so it's still the same hazard on the lower. However a kid can't get his finger caught while riding, so he hazard is limited to kids who undertake to work on bikes themselves.

If it's a concern, possibly you can improvise a chain disc attached to the chainring. Done right, this eliminates the worst of the hazard.

BTW- looking back o my childhood, chainguards were always getting caught on the crank arm and bent, eventually they were removed, and most of the heavily used kids bikes in my neighborhood were without halfway through the firs season.