My recommendation:
Begin training your child at about three years old. Don't give them a weapon, but create a situation that will teach them the basics. This may
sound stupid, but hear me out.
Give them a stick. Keep the stick in a safe or locked cabinet or cupboard. It helps if the stick has value (nicely shaped, carved, cured...) to make
it unique and worthy in the child's eyes. It helps if there is an implied power that has bad-guy whipping ability. Inevitably, the boogeyman or a
monster will sneak into the little one's closet or under the bed. When this happens, be patient. Use the stick to protect the child. Reinforce
that the stick is for protection only. Instruct the child in the basics of firearms. Since the stick is dangerous to boogeymen, it is also dangerous
to people. Never point the stick at anyone. Use it only when necessary. After use, make certain the child looks it over to ensure it is undamaged.
Allow them to clean/polish it once a week. If the little one has a vested interest in the stick's protection, it will go a looong way towards
setting up the basics. At age 3, it's a good idea to allow them to see YOU use it first. That way they'll know it works.
Eventually, the stick will begin to lose it's power. Children grow and boogeymen fade away. If they've learned the basics of safety properly, give
them a knife. Not for hunting or protection, but for WHITTLING. Provide them with a block of wood. (Cedar seems best) Explain that the same basic
rules still apply. This knife is used for a SPECIFIC purpose. Handle it with extreme care. Never point it at anyone (this may seem strange to you,
but the child will understand the significance.) Teach them how to be careful with it. The important lesson here is caution. A knife can be very
dangerous, but a child with knowledge of caution and who is supervised is a very good foundation for firearm training. I've learned that it's a
good idea to give them a long piece of wood (yew, cedar, or oak) and let them carve their own stick. It fulfills the child's memories and gives
them a familiar goal. The knife will then become a respected tool.
On my two oldest daughters, it was about 11 that I allowed them to start practicing with rifles. The groundwork for firearms training worked
extremely well for them. I've never given thought to people who can't legally handle firearms, though. Where would they go from there?
I would recommend fencing. Swordplay enhances response times, helps with the basics of strategy and tactics, and teaches discipline. With a rapier
(bobbed or not), safety is still considered very important. You can't teach them to aim, but you can teach them safety and proper usage.
To teach them HOW to use an actual firearm, play war with them. Give them wooden weapons, teach them how to use them as if they were real. Get them
accustomed to the weight, stances, sights, and appropriate use. If you need a real-world reason to do this, teach them some silent rifle drills. It
would blow your mind how fun rifle-drills are, and it will help you form a team bond with your kids. THeir discipline will be affected and if you
have drill competetions in the UK or wherever, it will give them a chance to complete, improve and be proud of their achievements.