Eureka! Here is an easy way to turn a coaster brake hub into a free hub!
Coaster brakes are a pain when trying to teach someone to ride a bike. Hand brakes are much better because then it is easy to turn a kids bike into a balance bike by removing the pedals and still allowing kids to stop their bike. With the pedals on it is better to allow new bicyclists to pedal backwards without causing a brake to engage. Coaster brakes make it harder for kids to learn, are not as effective as hand brakes, tend to cause more falls, and are also dangerous on bigger hills because they can overheat and fail.
Disabling a coaster brake hub so it is a free hub (no braking action) is pretty easy for just about anyone (and super easy for anyone who knows how to use a cone wrench). Warning: there is a lot of grease inside a coaster brake hub!
Before or as part of disabling the rear coaster brake, make sure you add a functional rear hand operated brake to the bike. Adding a rear hand brake may take a bit more skill to find brake levers that are good for kids as well as a rear caliper brake that works with your particular brake.
Simple steps to disable your coaster brake and turn it into a freehub:
Disconnect the coaster brake arm (remove but keep the screw that held it to the chain stay)
Take rear wheel off of bike
From the right (gear) side take off the axle nut, cone lock nut, & cone (leave the coaster brake arm side assembled)
Untwist the right rear sprocket (should be removable just with your hand)
Carefully pull out the inner gear assembly by holding onto the still attached coaster brake side of the axle and pulling it out of the wheel hub
Try to keep the bearings that are in bearing retainer clips in place by being gentle, if they fall out just remember to put them back in their correct locations
Remove and recycle the 2 loose curved pieces that should be stuck with grease to the outside of the inner cylinder from inside the coaster brake hub (these are the internal “brake pads”)
Pull off the inner cylinder (it will be covered with thick grease)
Bend out of the way or simply snip off the 2 thin prongs on a spring assembly that is at one end of the inner cylinder (easiest to do with the cylinder removed from the axle)
Put the cylinder back on the axle
Reassemble hub (without the 2 loose curved pieces) adjusting the cones and cone locknut as needed to turn smoothly without binding (easiest to do using cone wrenches)
Remount the rear wheel
Reattach the coaster brake arm to the chain stay even though it is no longer needed for braking action (the coaster brake arm remains a useful spacer as part of the hub assembly)
Verify your hand brake is properly adjusted and working
Voila! You can now pedal forward as usual as well as pedal backwards without worrying about any braking action!
The best video I have seen of how to do this is at https://www.youtube.com/watch?v=uI11KXFQPno. They bent the 2 prongs out of the way but I found it easy to snip them off with diagonal cutters. Googling “coaster brake to freehub” will locate other videos and instructions as well.
See also https://www.twowheelingtots.com/coaster-brake-vs-hand-brakes/