My son started at 6 got him a Hoyt Banshee at 7and got him in the saturday league at our local shop and shooting in the back yard. Insructional league,that really helped teach the basics, my son sometimes would get frustrated if he didn't think he was pleasing Dad he put undue pressure on himself. So it was nice to have someone else show him and then I helped him with other stuff. Plus the one guy is a national champ and his intructors are all state champs.
My son is 4 and my daughter is 5 they both want to go hunting with me now.
Take them especially scouting. That way they can learn about sign and the habitat and it peaks their interest. When you take them hunting you have to change your mind set some. You won't be hunting hard with young kids and they will want to move some and it's a good idea to have a secondary area,because they tend to not be able to sit for long peroids.
Taking the kids hunting got me out of hunting racks and made me just shoot deer for awhile. Couldn't let one walk whenI was with my son because it was very important to both of us that we took one together.When hegrunted in a 4 pt I was shooting it, tous that was huge.