With 5 kids who hunted now in their 20s and 30s, a couple of observations.
You can't start too early. You will have to taylor your hunt to their needs. They will each be different in desire and aptitude. The sooner you can figure out what they enjoy and then do it, the more they will enjoy it. You'll have more fun watching your kids hunt than hunting yourself. There is no pressure like guiding your own kids who have seen you come home from almost every hunt with something. You think a 4 hour car trip is a long time, a 10 hour hunting day can be entertaining. Thankfully there is a nap at noon.
They will learn more on a week hunting trip about life than in school for a semester. Take them out of school and go hunting. Take their friends with them, They are going to miss some trophy animals because of inexperience.
They will remember more adventures along the way, than actually harvesting the game. Good luck with fall sports and hunting. Kids will tell which one is more important to them. If you've ever driven all night after a Friday night football game to be on the horses at 4:30am to get where you want to be at daylight, it's worth it for your kids. Don't get caught up in the harvest, enjoy your time together. I say that with the caveat that all my kids killed elk, deer, turkeys and lots of other critters by age 12.
Enjoy the ride it will be over before you know it.