While ultimately, you have to decide which will work best for both him and you, we have had very young kids, even a 7 yo girl shoot our NRL22 matches. Since we are very much geared towards getting the younger shooters into and enjoying shooting sports, we only ever have them do things that fit within their physical capabilities.
Attention span is an issue, but nobody cares if they take a break and don’t shoot a stage or the whole match. Since they shoot for free at my matches, there is less stress than if they paid to attend. Parents are encouraged and even expected to assist them when they are very young and just starting. The rule book is for serious competitors as far as coaching and correcting aim on the clock. Plus, we encourage them to finish the stage even if time is up.
Then there is always a golf ball or full soda can stage that young and old, novice and experienced shooters alike enjoy.
Btw, I also do recommend steel challenge as a very accessible shooting match to newer shooters.
I will add that my daughter's have been shooting in local 22 prs style "outlaw" matches since they were 8 and 4. There is a strong push to get kids involved. There is a kids division and it is left up to the parents how much they help as long as everything is safe. When we started I would dial wind and elevation and move the gun from position to position. As they have gotten older, the 11 year old was dialing and holding wind in the reticle last year. Also, we stopped giving her corrections on the clock most of the time. The only thing I help her with now is I move the bag because she needs both hands to safely control a 15 lb gun and does not have the physical strength to move a heavy bag as well.
The little one is 7 now and she is learning to dial elevation. Holding in the retical is still a bit above her ability to understand cognitively.
We never really forced the time limits on them until they got good, and then we made them adhere to the time limits.
The club even writes a separate youth course of fire for stages with a lot of movement in the normal course of fire to help with not timing out and safety.
If you want to introduce him to prs style shooting it would be a good way if there is a club with similar attitudes near you. If you showed up at the club we shoot at, even if you had no gun, ammo, or any clue what you were doing, people would be falling all over themselves to let you borrow guns, ammo, and gear to participate.
Ultimately, you have to decide what is right for him and you. However, the worry that people will get annoyed or frustrated if you take the time to teach him and let him go slow and have fun is likely unfounded.