The age anyone can play this game depends on the insurance cover that each site has. Most sites in the UK, USA etc accept players from age 14, though many will also accept players as young as 10. I would advise that before playing Airsoft at any site, you make sure it has insurance cover for all players. Always wear eye protection when playing Airsoft, even if you are just playing in your backyard. It is not possible to convert these items to use anything other than little plastic BBs. Remember always play safe.