Lots to think about after all the input. I see @rookhawk jumped in with some awesome info. It really seems like I should be looking at 10 years old at the minimum. There's a lot of runway till then. My son might not be interesting in hunting at all?
The good news (for me) is my wife is all-in for a trip and sort of mentioned "we don't have to take the kid(s) right away." It sounds like she might be onboard for a husband/wife trip before before our son (or any future children) hit the suitable age to go.
If you'd permit me from going on a tangent @HookMeUpII and other readers.
We are facing serious constraints as a society with youths and the future of hunting. While I might claim from my vantage that I've found the "perfect age and perfect state of readiness" there are a lot of considerations.
The #1 problem related to global hunting is the aging out of viable hunters and fishermen. It's a particular crisis for the North American Conservation Model. You go to any event, lecture, or DNR function and 99% of the conversation is the "Three Rs". Recruitment, Reactivation, Retention.
So as pertains to kids, they have never been more distracted. Never have they been more sensitive. Never have they been less capable. Never have they been less resilient. That's a global societal truth.
By the time you think a kid might be ready to be introduced to hunting, you've probably missed the boat by 4-8 years. Sitting in the cold in a stand waiting for a deer for 8 hours is somehow not as interesting as sitting on a phone or xbox all day talking to fake friends. Hunting is no more or less exciting than it was 20,000 years ago, but technology is calibrated to trigger endorphins in the brain in a way that wasn't even considered 15 years ago. Modern tech is designed to be as effective as heroine.
For high performing, high-flyer kids, education has never been more competitive. If your kids are caucasian, east asian, or indian, the odds of them getting into a good school are very, very low. Thus, the notion of getting that kid at say age 12-14 to become interested in hunting is pretty darned slim, they have good cause to be obsessed with education because the challenge of getting ahead has never been harder.
So what do we do?
My opinion is 1.) Greatly restrict technology. 2.) Introduce children to hunting VERY early. 3.) Demand excellence with ever-moving goal posts and challenges to bring them to the brink of tears from defeat, but judge it well enough that they succeed. Keep stretching their coping skills and their difficulty levels. In short, make very hard things become fun things by habit for your kids. 4.) Fund their hunting dreams because a modern kid isn't going to ask over and over again, you either create a garden for them to flourish or they will pivot to the easy/lazy interests of modern youth. 5.) Govern over and limit your kids extra-curricular activities so there is still time for hunting and the required 2 sports and 2 clubs per year formula for them to have a chance to get into a reasonable college.
If your kids aren't hunting by 6-7 years old, big game hunting by 8-10, and bird hunting by 10-12, I think you're going to have big problems you couldn't have foreseen. You cannot measure your kids against your own childhood, nothing about the current era matches the olden days.
The problem we have as adults is we assume past methods and parenting approaches will work with the latest generation of children. It will not. The forces working against kids today is nothing like it was for Greatest Generation, Baby Boom, or Gen X adults.
If you're not spending 20 hours a week planning, preparing, enjoying, or practicing with your kids related to hunting, you're falling behind in a game that you may not be able to recover later on.
Related to the three Rs, you can reach people at three times in their lives: 6-10 years old, 28-35 (after school, career start, marriage), and again at 50-60 (peak earnings, empty nesters, free time returns).
By the numbers, if you don't get 6-10 year olds obsessed, they will be unlikely to retain, and they won't even have a shot to reactivate in your lifetimes.