I’m sure if I asked the parents of the kids if they could ask them to wait til after 9am to play on the go kart they probably would, I have a lower expectation of “polite” behaviour from kids and I don’t want to take their fun away from them, you’re only young once and I don’t really begrudge them it.
For vehicle exhaust, we’re basically already solving the problem by moving away from ICE vehicles, so I don’t see the reason in arguing about it.